Focus module and components with actuator polymer control

ABSTRACT

A focus module containing a boundary element and a focus element. The focus element includes a fluid and a deformable membrane, with the fluid being entrapped between the boundary element and the deformable membrane. The focus module also includes a pressure element, which is capable of deforming the focus element by pressing on the deformable membrane in the direction of the boundary element.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to and the benefit of co-pending U.S.provisional patent application Ser. No. 60/875,245, filed Dec. 15, 2006.

This application is related to U.S. patent application Ser. No.60/778,569, filed Mar. 2, 2006, entitled “Data reader apparatus havingan adaptive lens”; co-pending U.S. patent application Ser. No.11/521,142, filed Sep. 14, 2006, entitled “Data reader apparatus havingan adaptive lens”; and co-pending U.S. patent application Ser. No.11/546,531, filed Oct. 11, 2006, entitled “Control system for adaptivelens”.

The disclosures of all the foregoing applications are herebyincorporated in their entireties by reference thereto.

FIELD OF THE INVENTION

The invention relates generally to focus modules, and more specificallyto focus modules in which focus control involves use of electricallyactuated polymer.

BACKGROUND OF THE INVENTION

In brief, a fluid lens, sometimes also referred to as an adaptive lens,comprises an interface between two fluids having dissimilar opticalindices. The shape of the interface can be changed by the application ofexternal forces so that light passing across the interface can bedirected to propagate in desired directions. As a result, the opticalcharacteristics of a fluid lens, such as whether the lens operates as adiverging lens or as a converging lens, and its focal length, can bechanged in response to the applied forces.

Fluid lens technology that employs electrical signals to control theoperation of the fluid lens has been described variously in Matz, U.S.Pat. No. 2,062,468; Berge et al., U.S. Pat. No. 6,369,954; Onuki et al.,U.S. Pat. No. 6,449,081; Tsuboi et al., U.S. Pat. No. 6,702,483; Onukiet al., U.S. Pat. No. 6,806,988; Nagaoka et al., U.S. Patent ApplicationPublication No. 2004/0218283; Takeyama et al., U.S. Patent ApplicationPublication No. 2004/0228003; and Berge, U.S. Patent ApplicationPublication No. 2005/0002113, as well as International PatentApplication Publications Nos. WO 99/18546, WO 00/58763, and WO03/069380.

Additional methods of controlling the operation of fluid lenses includethe use of liquid crystal material (Nishioka, U.S. Pat. No. 6,437,925),the application of pressure (Widl, U.S. Pat. No. 6,081,388), the use ofelastomeric materials in reconfigurable lenses (Rogers, U.S. Pat. No.4,514,048), and the uses of micro-electromechanical systems (also knownby the acronym “MEMS”) (Gelbart, U.S. Pat. No. 6,747,806).

Further attempts to develop fluid lens control modules may be see in,for example, Sasaya et al., U.S. Pat. No. 6,188,526; de Luca, U.S. Pat.No. 3,161,718; Flint, U.S. Pat. No. 2,300,251; Yao et al., U.S. PatentApplication Publication No. 2005/0014306; O'Connor et al., U.S. PatentApplication Publication No. 2005/0100270; Massieu, U.S. PatentApplication Publication No. 2005/0218231; Michelet, U.S. Pat. No.4,289,379; Viinikanoja, U.S. Pat. No. 6,936,809; European PatentApplication EP 1 674 892 A1; British Patent Specification GB 1327503;Japanese Pat. No. JP2002243918 (Olympus Optical, Application No.JP20010037454); and International Patent Application Publication No. WO03/071335.

Further examples include Shahinpoor, U.S. Pat. No. 5,389,222; Shahinpooret al., U.S. Pat. No. 6,109,852; Guy, U.S. Pat. No. 6,542,309; Pelrineet al., U.S. Pat. No. 6,376,971; Ren H., Fox D., Anderson A., Wu B., andWu S-T, 2006, “Tunable-focus liquid lens controlled using a servomotor”, Optics Express 14(18):8031-8036; Santiago-Alvarado A,Gonzalez-Garcia J, García-Luna J, Fernández-Moreno A, and Vera-Díaz W,2006, “Analysis and design of an adaptive lens”, Proceedings of SPIEOptics and Photonics 6288:62880S-1-62880S-8; Ghosh T K, Kotek R, andMuth J, 2005, “Development of layered functional fiber basedmicro-tubes”, National Textile Center Annual Report 1-9; Pelrine R,Kombluh R D, Pei Q, Stanford S, Oh S, Eckerle, J, Full R J, Rosenthal MA, and Meijer K, 2002, “Dielectric elastomer artificial muscleactuators: toward biomimetic motion”, Proc. SPIE 4695:126-137; ChronisN, Liu G L, Jeong K-H, and Lee L P, 2003, “Tunable liquid-filledmicrolens array integrated with microfluidic network”, Optics Express11(19):2370-2378; each of which is incorporated herein by reference inits entirety.

However, there is a continuing need for improved systems and methods forusing fluid lenses in present day systems.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects and features of the invention can be better understood withreference to the drawings described below, and the claims. The drawingsare not necessarily to scale, emphasis instead generally being placedupon illustrating the principles of the invention. In the drawings, likenumerals are used to indicate like parts throughout the various views.

FIG. 1 is an exploded view of one embodiment of a focus module;

FIG. 2 is the focus module of FIG. 1 as viewed from the right side;

FIG. 3 is the focus module of FIG. 1 as viewed from the left side;

FIGS. 4 a and 4 b show the effect of pressure exerted on the focusmembrane in a direction substantially normal to the plane of the focusmembrane;

FIGS. 5 a and 5 b show the effect of pressure exerted on the focusmembrane in a direction substantially parallel to the plane of the focusmembrane;

FIG. 6 is a view of the deforming element;

FIG. 7 shows the focus fluid having a non-symmetric meniscus;

FIG. 8 shows a cylindrical component of the focus module;

FIGS. 9 is a side perspective showing convex distortion of the topsurface of a cylinder having a fluid interior volume in response to areduction in height of the cylinder;

FIG. 10 is a side perspective showing convex distortion of the topsurface of a cylinder having a fluid interior volume in response to areduction in diameter of the cylinder;

FIGS. 11 a and 11 b illustrate the deforming element as it deforms fromthe initial shape shown in FIG. 11 a to that in FIG. 11 b by verticalcontraction/horizontal elongation;

FIG. 11 c shows the deforming element assuming a funnel-like shape;

FIGS. 12 a-12 d show various ranges or directions of motion for thedeforming element;

FIGS. 13 a and 13 b show a bi-convex electro-actuated polymer membranelens;

FIG. 14 shows a lens assembly incorporating multiple deformable focusmembranes;

FIGS. 15 a and 15 b show a conventional lens with an electro-actuatedpolymer deforming element;

FIG. 16A is a diagram showing a reader;

FIG. 16B is a diagram showing the control circuitry of the reader ofFIG. 16A in greater detail;

FIG. 17 is a block diagram of an optical reader showing a generalpurpose microprocessor system that is useful with various embodiments ofthe invention;

FIG. 18 is a flow chart showing a process for operating a system havingan adjustable focus system comprising feedback;

FIG. 19 is a flow chart showing a process for operating a system havingan adjustable focus system that does not comprise feedback;

FIG. 20 is a circuit diagram showing a commutating power supply for afluid lens system;

FIG. 21 is a timing diagram showing a mode of operation of thecommutating power supply of FIG. 20;

FIGS. 22 a and 22 b are drawings of hand held readers;

FIG. 23 is a diagram of a handheld reader in communication with acomputer;

FIG. 24 is a flow chart of a calibration process useful for calibratingapparatus embodying features of the invention;

FIG. 25 is a diagram showing calibration curves for a plurality of handheld readers;

FIG. 26 is a diagram showing an embodiment of a power supply suitablefor use with hand held readers;

FIG. 27 is a timing diagram illustrating a mode of operation of a handheld reader;

FIGS. 28 a-28 c are cross-sectional drawings showing a fluid lens with amount comprising an elastomer for a hand held reader;

FIG. 29 is a diagram illustrating a prior art variable angle prism;

FIG. 30 is a cross-sectional diagram of a prior art fluid lens that isdescribed as operating using an electrowetting phenomenon;

FIG. 31 a is a cross sectional diagram 2400 showing an embodiment of afluid lens configured to allow adjustment of an optical axis;

FIG. 31 b is a plan schematic view of the same fluid lens;

FIG. 32 is a schematic diagram showing the relationships between a fluidlens and various components that allow adjustment of the optical axisdirection;

FIG. 33 a is a schematic diagram of an alternative embodiment of a fluidlens;

FIG. 33 b is a schematic diagram of an alternative embodiment of adistributor module;

FIG. 34 is a schematic diagram showing the relationship between a fluidlens and a pair of angular velocity sensors;

FIGS. 35 a-35 e are cross-sectional diagrams of another prior art fluidlens that can be adapted for use according to the principles of theinvention;

FIG. 36 is a schematic block diagram showing an exemplary drivercircuit;

FIGS. 37A and 37B are diagrams that show an LED die emitting energy in aforward direction through a fluid lens; and

FIGS. 38A, 38B and 38C show diagrams of a laser scanner comprising alaser 3110, a collimating lens 3120, and a fluid lens 3130 in variousconfigurations.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides a focus module for use in a fluid lensthat in particular has few moving parts and does not require thepresence of multiple chambers or reservoirs for the fluid component ofthe lens.

More particularly, the present invention is directed to a focus modulewhich may include the following elements:

-   -   1) a boundary element, which may be rigid (such as glass or        plastic) or deformable (such as elastomer);    -   2) a spacer element, interposed between the boundary element and        focus element;    -   3) a focus element, deformable in at least one dimension (such        as a fluid or elastomer);    -   4) a pressure element, which transmits force from the deforming        element to the focus element;    -   5) a deforming or actuator element (such as artificial muscle or        electrically actuated polymer) to act upon the focus element;    -   6) a conductor element for conducting an electrical signal or        stimulus to the deforming element;    -   7) a housing element to provide a physical housing or anchor for        the assembly; and    -   8) a power source, generally located external to the focus        module, for powering the conductor element.

As will be explained further herein, not all of these elements arerequired for an operable focus module. For example, the deformingelement may also function as the spacer element; the spacer element maybe omitted, as when the lens is provided by use of a unitaryfluid-filled element as discussed hereinbelow; the pressure element maybe omitted, with the deforming element acting directly on the focuselement; and the housing element is essentially a container into whichthe other elements may be placed, or in which they may be assembled, andwhose function may be provided by other structural elements in theapparatus or device in which the focus module is to function.

The boundary element may be rigid, such as glass or plastic, ordeformable, such as an elastomer. When it is desired that the boundaryelement not undergo any deformation as a result of deforming force beingapplied to the focus element, it is sufficient if the elasticity of theboundary element is such that the boundary element will not deform inresponse to the force or energy that will be communicated to it when thefocus element is at maximum deformation. For example, if the focusmodule includes a boundary element, spacer element, and focus element,with the focus element comprising a fluid and a deformable membranewhere the fluid is entrapped between the boundary element and themembrane; and, a pressure element is used to deform the focus element byexerting pressure on the fluid, whether by pressing on the membrane inthe direction of the boundary element or by decreasing the diameter ofthe fluid space between the boundary element and the membrane (forexample, by annular tightening); if it is desired that the boundaryelement not deform, then it should be sufficiently rigid to remainplanar when the pressure element is exerting maximum pressure on thefluid. In other words, when it is desired that the boundary element notdeform during operation of the focus module, it is necessary only thatthe boundary element not deform under such conditions, and not that itbe completely rigid or incapable or deforming.

As stated, glass may be used, and a variety of optical glass materialsare commercially available, including, for example, Corning® EAGLE2000™Display Grade glass, available from Coming Display Technologies,Corning, N.Y. USA, and N-BK7 glass, available from Schott North America.Inc., Duryea, Pa. USA. The boundary element may be any suitablethickness, including from about 0.1 mm to about 1 mm, for example, 0.2,0.3, or 0.4 mm.

The spacer element may be any of a variety of materials, includingmetal, plastic, and ceramic, depending on its desired functionality.When that functionality is limited to spacing the boundary element fromthe focus element it may be any material that is compatible with theother materials it will contact, including the focus fluid, such asstainless steel. When it is also desired to provide a seal betweenitself and the boundary element and/or the focus element, the spacer maybe a two-sided tape. When it is desired to serve as the deforming oractuator element it may be an artificial muscle or electro-actuatedpolymer as discussed further herein. When the spacer element is desiredto both seal to the boundary and/or focus elements and serve as thedeforming or actuator element, it may be a double sided tape thatadditionally provides a deforming or actuator function in response toelectrical stimuli; for example, a 3M™ VHB™ tape such as Double CoatedAcrylic Tape 4910, available from a number of distributors, includingHillas Packaging, Inc., Fort Worth, Tex., USA.

In order to facilitate filling of the fluid chamber with focus fluid, agap or port may be present in the spacer element, shown in FIG. 1 aselement 2 a. After the fluid chamber has been filled with focus fluid,this gap or port may be sealed by any means that will both prevent fluidfrom escaping the chamber, and will withstand the pressure subsequentlyexerted by the focus fluid as in response to actuation of the deformingelement. For example, an epoxy adhesive may be used to provide thisseal.

The focus element may be a single component, such as afluid-filled-filled elastomer, polymer, or plastic; for example, atransparent oil-filled elastomer material which has an elastic memory.Alternatively, the focus element may be two or more components, with afocus fluid (such as water or oil) entrapped or sandwiched between theboundary element and a deformable focus membrane, in which configurationthe focus fluid and the focus membrane would together comprise the focuselement. When a membrane is used, suitable materials would includepolydimethylsiloxane, or PDMS, such as Sylgard® 184 silicone elastomer,available as a kit from Dow Corning Corporation, Midland, Mich., USA.The membrane thickness may be selected based on factors such as the sizeof the focus module in question and may be, for example, from about 0.1to about 1 mm, for example, 0.2, 0.3, or 0.4 mm.

When a focus fluid is used, its properties should be selected forcompatibility with the other materials, stability under use, tolerancefor the anticipated temperatures at which it will be used, and similarfactors. Optical fluids and optical grade oils, such as optical grademineral oils, may be used. One suitable optical fluid is Type Aimmersion oil, available from Cargille-Sacher Laboratories Inc., CedarGrove, N.J., USA. Another suitable fluid is the Santovac® polyphenylether-based optical fluid SL-5267, available from Arch TechnologyHolding LLC., St. Charles, Mo., USA. Water may also be used, such asdeionized water.

As previously noted, the boundary element and focus element must beoptically clear, at least in that portion thereof used to transmit imageinformation. Thus, while the entirety of each such element wouldnormally be optically clear in order to simplify manufacture andassembly, it is also possible for at least a part of an outer ringportion of either or both of the boundary element and focus element tobe translucent or opaque, surrounding an inner portion that is opticallyclear.

When it is desired to minimize loss of light transmitted through thefocus module due to reflection loss, the materials selected for theboundary element and focus element should have similar indices ofrefraction. For example, where the focus module includes a glassboundary element, a focus fluid, and a focus membrane, one shouldconsider the difference in indices of refraction both of the focus fluidcompared to the boundary element, and of the focus fluid compared to thefocus membrane. The greater the difference in indices, the more lightwill be loss to reflection as it attempts to pass from one material(such as glass) to the next (such as an immersion oil). Conversely, thecloser the indices, the less light will be lost to reflection. In thiscontext the indices will ideally identical, and preferably will bewithin about +/−0.001 to 0.01, such as about 0.002. However, there maybe situations where differences in the indices of refraction may beadvantageous, such as to reduce certain types of aberrations.

It is also possible to vary the thickness of the focus membrane over thedeformation area, which would result in a structure having asphericattributes while retaining the variability otherwise enabled by thepresent invention.

Choosing a focus fluid with a relatively high index of refraction willreduce the amount of deformation needed to obtain a given change infocal distance. For example, a suitable index of refraction would be inthe range of from about 1.3 or about 1.5 to about 1.6 or about 1.7, suchas an index of about 1.5 or about 1.6.

The pressure element may similarly be any of a variety of materials,including metal, plastic, and ceramic. The choice of material willdepend on compatibility with other materials and on the desired responseto force exerted by the deforming element. If it is desired that thepressure element not itself deform, it should be an inelastic materialsuch as metal, ceramic, or plastic. If, however, it is desired ornecessary that the pressure element change its shape or configuration inresponse to the deforming element, it should be composed of a deformablematerial such as an elastomer.

The deforming element is the component that responds to a control signalby varying the force applied to the focus element, either indirectly(such as through the pressure element) or directly. Particularlysuitable for use as the deforming element are electroactive orelecroconducting polymer actuators. One example is Electroactive PolymerArtificial Muscle and/or the Universal Muscle Actuator™ platform,available through Artificial Muscle, Inc., of Menlo Park, Calif., USA.Another example is conducting polymer actuator available from EAMEXCorporation of Osaka, Japan.

Where the deforming element is an artificial muscle or electro-actuatedpolymer, it may be possible to provide the deforming element as two ormore layers, analogous to layers of muscle fiber. Moreover, where eachlayer deforms in a particular direction in response to electricalstimuli, this effect may be used to select a given direction of motionfor the overall layered assembly. In this way, and taking for example adeforming element in which layers of artificial muscle of polymer havebeen assembled into the shape of a rectangular solid as shown in FIG. 12a, the rectangular solid may then curl up as shown in FIG. 12 b, extendlaterally as shown in FIG. 12 c, or curl down as shown in FIG. d, oreven twist, in response to electrical stimuli, though use of anon-elastic structure to constrain one or more directions of motion, orto force the motion in a particular manner, may be required. FIGS. 12 band 12 d depict non-uniform curvature of the rectangular solid, whichcould be accomplished by constraining a portion of the rectangular solidsuch as by a frame or other external structure (not shown), by anchoringor fixing a portion of the solid to an inelastic element, or byappropriate construction or selection of the layers which comprise thesolid. Alternatively, the rectangular solid may exhibit a constantradius of curvature along its length, for example, the curve formed by alonger side may represent an arc along the circumference of a circle.Where multiple electrical circuits are present in the deforming element,the electrical stimuli may include applying voltage to less than all ofthe circuits, and/or applying voltage of opposite polarities to thosecircuits.

These changes in shape may further be accomplished by layering asdescribed, with each layer, or combinations of layers, having its ortheir own electrical control circuit; or, the deforming element may beconstrained by a frame or other structure that limits its motion in oneor more direction, thereby forcing movement in the desired direction.Similar effects may be accomplished by making the layers of unequaldimension; for example, in a two-layer structure, if one layer is longerthan the other in a particular dimension, then actuation of the layerswill generally produce curling in the direction of the shorter layer.This mode of action may be better understood by reference to deformingelement 5 as shown in FIGS. 1, 2, and 6; in FIG. 6, for example, thefinger or tab-like elements 5 a may function by containing two or morelayers of polymer, with the layers closer to the focus membrane beingshorter than those closer to the boundary element. When deformingelement 5 is activated, this difference in the size or dimensions of thelayers will cause each finger element 5 a to curl or flex towards thepressure element, forcing it in the direction of the focus membrane, andthis motion will in turn deform the focus membrane into the shape of aconvex lens. Alternatively, a non-deforming layer may be included in thestructure, in which case the deforming layer or layers will generallycurl or move towards or in the direction of the non-deforming layer.

FIGS. 13 a and 13 b demonstrate a bi-convex electro-actuated polymermembrane lens. In this embodiment, when both surfaces are deformablemembranes, it is possible to construct a bi-convex lens. Moreover, thetwo surfaces of the membranes may have different surface curvatures dueto different membrane diameters. Differences in the material, andthickness, of the membrane can also be used to create different surfaceshapes.

FIG. 14 shows a multiple deformable membrane lens assembly, and itshould be noted that a zoom lens can be achieved using two (or more)lenses actuated by electro-actuated polymer and other fixed elements.

FIGS. 15 a and 15 b show that by placing a conventional lens in anelectro-actuated polymer mechanism, a variable location lens element canbe made for compact auto-focus or zoom applications, with additionalfixed elements.

As noted, the deforming element may act directly on the focus element,as by being in direct contact with it. Alternatively, force generated byactivation of the deforming element may be transmitted to the focuselement through one or more intermediary devices or elements. As anexample, a pressure element may be adjacent to and in contact with thefocus element, and the deforming element may press on the pressureelement, which transmits that force through to the focus element. In oneembodiment the pressure element may be in the shape of an annulus, ordoughnut, and may be in direct or indirect contact with an outer ringportion of the focus element.

The conductor element communicates the control signal to the deformingelement. Where the deforming element responds to electric signals, as inthe case of electro-actuated polymers, it generally serves as aconductor for conducting electrical motive power from the power sourceto the deforming element. It should therefore be conductive, preferablyhighly conductive, at least in relevant portions, and may comprise aconductive material, including a conductive metal such as copper; aconductive plastic; or an elastomer that has been treated or doped, suchas with carbon, to render it conductive. Specific examples include useof flexible printed circuits (FPC) and sputtering or evaporating aconductive metal onto the surface of the deforming element.

As depicted in FIG. 1, the conductor element comprises two components,one on either side of the deforming element, with each component havingan electrical contact access 6 c for connection to a power source. Inthis embodiment the deforming element will be uniformly activated ordeactivated in response to the presence or absence of an electricalsignal, and the convex meniscus formed by the focus element will besymmetrical.

However, it is also contemplated that the conductor element may includea plurality of circuits enabling selective actuation of one or moreportions of the deforming element, thereby allowing tunable steering ofthe focus element by enabling the convex meniscus to be selectivelyasymmetric. For example, and with reference to FIG. 6, the deformingelement is shown as a single conductive element. Alternatively, thedeforming element could be constructed, such as by the use of insulatingmaterials between flex circuits, such that each finger (also shown aselements 5 a in FIG. 2), or combinations thereof, provide separate andindependently energizable circuits.

By choosing which circuits to energize, and how much control signal toapply, the system could control not only the formation and magnitude ofthe meniscus, but also its tilt. In this context, tilt refers to thepossible combinations of pitch and yaw that may be used to configure themeniscus to have shapes other than symmetric to an axis normal to theboundary element and centered in the fluid chamber. A simple example isshown in FIG. 7, in which focus fluid 3 b has been further representedas having meniscus element 3 c, shown as having a non-symmetric shape inresponse to selective application of control signals to a multi-circuitconductor element (not shown).

The conductor element is connected to a power source selected to deliverthe range and polarity of voltage necessary to drive the deformingelement through its full intended range of motion.

The figures may be referenced to provide further context for the abovediscussion, it being understood that they merely present one specificconstruct of the focus module as a convenience for purposes of the thisdiscussion.

In particular, FIG. 1 provides an exploded view of one embodiment of thefocus module. In this embodiment, spacer element 2 creates aspaced-apart relationship between boundary element 1 and focus element3. Pressure element 4 rests against focus element 3, and is acted on bydeforming element 5, which is itself acted on by conductor element 6. Inthe embodiment shown, conductor element 6 comprises two sub-elements 6 aand 6 b, which are conductive elements used to transmit electricalcontrol signals to deforming element 5. Element 6 c is an electriccontact access for conductor element 6. A complementary electric contactaccess is present on element 6 a, but is not visible in FIG. 1. Element7 is a housing element, and serves to provide a physical environment forthe focus module.

FIGS. 2 and 3 show the focus module embodiment of FIG. 1 in assembledform, in which housing element 7, electrical contact element 6 c,deforming element 5, and pressure element 4 are most visible. In theperspective of FIG. 2 the assembled focus module is viewed from theright side of FIG. 1, with the boundary element closest to the viewer,and in FIG. 3 the assembled focus module is viewed from the left side ofFIG. 1.

The overall size of the assembled focus module is not critical and maybe varied depending on the size of the available components, the deviceinto which it will be placed or assembled, and the needs of the user. Ingeneral, the focus module, which is generally cylindrical as shown inFIGS. 2 and 3, will have a diameter d of from about 5, 7, or 9 mm to aslarge as about 11, 13, 15, or 20 mm. The size may be selected in orderto maximize or achieve drop-in compatibility with existing devices; forexample, in camera-enabled cellular telephones, a diameter of about 9,9.5, or 10 mm may be preferred.

For purposes of example, FIGS. 4 a and 5 a each depict an assemblyincluding a boundary element 1, focus fluid 3 b, focus membrane 3 a, anddeforming element 5. In FIGS. 4 a and 5 a, minimal pressure is beingapplied to focus fluid 3 b, and focus membrane 3 a is correspondinglyplanar. In FIGS. 4 b and 5 b, pressure is being applied by deformingelement 5 to focus fluid 3 b, and as a result focus membrane is forminga convex lens or meniscus. In FIG. 4 a the pressure applied by deformingelement 5 is exerted in a direction substantially normal to the planerepresented by focus membrane 3 a and in the direction of boundaryelement 1, reducing the height of the chamber containing the focus fluidaround its circumference and thereby forcing fluid from the periphery ofthe fluid chamber into the middle; this effect produces the convexmeniscus visible in FIG. 4 b.

As previously noted, the deforming element may act on the focus elementdirectly or indirectly. Also as previously indicated, direct action mayinvolve placing the deforming element directly adjacent the focuselement, for example, directly contacting the focus membrane when thefocus element is comprised of a focus membrane and a focus fluidentrapped between the focus membrane and the boundary element, with aspacer element defining the wall of a chamber holding the focus fluid.In an alternative embodiment, the deforming element may itself comprisethe wall separating the boundary element and the focus membrane. Thisembodiment is shown in FIG. 5 a, where deforming element 5 is alsoserving as the wall of the cylindrical chamber containing the focusfluid 3 b, that chamber having a ‘top’ wall formed by the focus membrane3 a and a ‘bottom’ wall formed by the boundary element 1.

In this embodiment the pressure exerted by deforming/spacer element 5 isexerted in a direction substantially parallel to the plane representedby focus membrane 3 a and in the direction of the middle of the fluidchamber. Depending on the characteristics of the material used for thedeforming element, this pressure may not be accompanied by any change inheight of the fluid chamber, and the deforming element may simplyincrease its thickness radially. Alternatively, the extension of thedeforming element radially inward may be accompanied by a decrease inheight or thickness of the deforming element inward as shown in FIG. 5b, effectively drawing focus membrane 3 a and boundary element 1 towardseach other and contributing to the formation of the convex meniscus; notonly is the inward radial movement of the deforming element forcing thefocus fluid to occupy a smaller-diameter cylinder, but thedrawing-together of the focus membrane and boundary element are alsoreducing the height of that cylinder.

More generally, and with reference to FIG. 8, the focus module mayinclude a cylinder 100 having at least a top surface 101, a bottomsurface 102, an outer wall 103, a fluid interior volume 104, thecylinder having diameter d and height h. When the actuator element isexternal to this structure it will exert pressure on at least one of thetop surface, bottom surface, or outer wall in order to reduce one orboth of height h and diameter d. Because the contents of the fluidinterior volume are incompressible, this reduction in height and/ordiameter must be offset by a corresponding expansion of the volume insome direction which, in the case of the focus module, will involvedeformation of one or both of top surface 101 and bottom surface 102.FIGS. 9 and 10 provide a simplified, straight side-on view of thiseffect. In particular FIG. 9 provides an illustration of deformationcaused by a reduction in height, with the cylinder now having the samediameter d but height h′<h, and FIG. 10 provides an illustration of adeformation caused by a reduction in diameter, with the cylinder havingthe same height h but diameter d′<d; neither illustration is necessarilyto scale. In both of these illustrations the deformation andcorresponding change in one dimension if offset by a convex distortionof the top surface 101. In these embodiment the deforming or actuatorelement may be exerting pressure on the fluid interior as shown in FIGS.1-5. Of course, both the diameter and the height may be changed at thesame time, and this could be used to produce a relatively largermeniscus, and/or to decrease the time required to form the meniscus.

Alternatively, the deforming or actuator element may comprise part orall of outer wall 103, as show in FIGS. 11 a and 11 b. Here the cylinderis shown in cross-section to illustrate the annular nature of deformingelement 5. In FIG. 11 a the upper deformable surface (not shown) will beplanar, while in FIG. 11 b the deforming element has responded toactuation by contracting in the vertical or “h” dimension and extendingor elongating in the horizontal or “d” dimension. In FIG. 11 b theeffect is shown with the deforming element drawing the upper and lowersurfaces together uniformly over their entire surface area, whichrequires that the exterior circumference of one or both be verticallymoveable or slideable rather than fixed or anchored. (In thisdiscussion, directional references such as “horizontal”, “vertical”, andthe like are generally used in the relative rather than absolute sense,with, for example, vertical referring to the direction defined by a linenormal to the top and bottom surfaces when both are planar, andhorizontal referring to the direction defined by a line parallel tothose surfaces when both are planar.) However, it is also contemplatedthat at least one surface or surface edge will be anchored or fixed,which will result in a different effect when the deforming elementchanges its dimensions. For example, and with reference to FIG. 11 b, ifthe top surface is deformable while the bottom surface is rigid, and theouter circumference of the cylinder is constrained such as by beingcontained within a ring of metal, ceramic, or other rigid material,movement of the deforming material to contract or compress in thevertical dimension and to extend or elongate in the horizontal dimensionwill not be uniform and symmetrical, but may, for example, result in afunnel-like shape as shown in FIG. 11 c.

It should be noted that it is equally possible to construct the focusmodule to produce a concave lens. For example, the pressure ring anddeforming element could be positioned under the focus membrane, betweenthat membrane and the spacer element, and activation of the deformingelement could increase, rather than decrease, the height of the fluidchamber around its circumference or periphery. The same effect would beachieved if the deforming element also served as the spacer element, asdiscussed elsewhere herein, with the pressure element positioned betweenthe deforming element and the focus membrane. The pressure element neednot be present, in which case the deforming element would act directlyon the focus membrane.

Another concave lens embodiment may be considered in reference to aparticular method of preparing and filling the fluid chamber. First, oneor more boundary elements, such as glass plates, are placed in recessesprovided in a support structure such as a metal plate. Spacer elements,such as double-sided tape, are then placed on each glass plate. Next, asheet or layer of PDMS is placed over the glass plate-spacer elementassemblies; this sheet may, for example, be prepared by spin-coating thePDMS to a desired thickness using known techniques. The resultingassemblies of glass plate boundary element, spacer element, and PDMSmembrane element are then placed under vacuum, focus fluid is added, andthe vacuum is released to draw the focus fluid into the fluid chambers.If this filling process is stopped before the fluid chambers arecompletely filled, the initial shape of the focus membrane will beconcave. Depending on the degree of concavity selected, and theparameters chosen for the rest of the focus module, the resulting modulemay function only by varying the degree of concavity of the focuselement, or may be capable of deforming the membrane from a concavestate to a flat state, and even of deforming it beyond a flat state to aconvex state.

The deforming element has an active and passive state, depending onwhether or not a control signal is being applied, and has a continuoustransition between the two states, preferably in linear response to thestrength of the control signal. Using “deactivated” to describe thestate of the deforming element when the control signal is at zero orminimal input, and “activated” to describe the state of the deformingelement when the control signal is applied, the system may be configuredeither such that the deactivated state is when maximum force is beingapplied to the focus element, or when minimal force is being applied.

Therefore, FIGS. 4 a and 5 a may be characterized as representingdeactivated states, the system being configured such that the deformingelement is communicating minimum force to the focus fluid when nocontrol signal is being applied, and FIGS. 4 b and 5 b may representactivated states, in which a control signal is being applied to energizethe deforming element. However, it is possible also configure the systemin the opposite sense, so that FIGS. 4 a and 5 a represent that state ofthe system when the control signal is being applied, and FIGS. 4 b and 5b represent its state when the control signal is at zero or minimalstrength. In more common terms, the deforming element may either berelaxed (as in FIGS. 4 a and 5 a) when the power is off and stretched orexpanded (as in FIGS. 4 b and 5 b) when power is on, or vice versa. Thisgenerally translates into what the desired ‘resting’ state of the focusmodule should be. When the focus membrane is planar the focus is set toinfinity, and when it is convex the focus is at a finite distance, suchas from about 5 mm to about 500 mm, including all points there between,such as about 50, 100, 150, or 200 mm. Configuring this aspect of thesystem may therefore depend on whether the user wishes the ‘normal’ or‘resting’ state to be focused on infinity, or closer in.

While the foregoing discussion has been presented in the context of afocus element comprised of a focus fluid and focus membrane, it is alsoapplicable to the alternative embodiment where the focus element isunitary, as in the case of a fluid-filled/oil-filled elastomer. In thisembodiment, the outer surface of the focus elastomer provides thefunction of the focus membrane, and the interior of the focus elastomerprovides the function of the focus fluid.

The deforming element and related assembly of the present invention mayalso be used to control motion of a conventional, rather than fluid,lens. It is further possible to combine the focus module of the presentinvention with one or more conventional or fluid/adaptive lenses, and/orwith one or more other focus modules. In this way furtherfunctionalities such as zoom or autozoom may be realized. These andrelated concepts are further described in the Appendix being filedcontemporaneously with this disclosure.

The focus module may be used in a wide variety of devices having orusing imaging capabilities, including data collection devices such asbar code scanners, portable data terminals (PDTs), portable dataassistants (PDAs), camera-enabled cellular telephones, still picturecameras, moving picture cameras, and the like, further including bothfixed-mount and portable devices. The focus module may be used in anysize and type of such device, but due to its small size and minimal useof moving parts, it is especially well-suited for devices where minimaluse of space is particularly desirable, and/or where ruggedization isdesired against shock, vibration, and other environmental influencesthat could affect the operability and/or effective lifespan ofcomponents having more and/or more delicate moving parts.

As one particular but non-limiting example, the present invention may beapplied to apparatus and methods useful for imaging, capturing, decodingand utilizing information represented by encoded indicia such as barcodes (for example, 1D bar codes, 2D bar codes, and stacked bar codes),optically recognizable characters (for example printed, typed, orhandwritten alphanumeric symbols, punctuation, and other OCR symbolshaving a predefined meaning), as well as selected graphical images suchas icons, logos, and pictographs. The apparatus and methods involve theuse of one or more focus modules with data readers such as hand held barcode readers to accomplish such tasks as imaging barcodes and otheroptically readable information, including focusing on images ofinterest, and improving image quality by removing artifacts such asjitter introduced by a user who is manually operating a reader of theinvention.

The device which bas been described and which has been termed a liquidlens of variable focal length has many other applications. It may beemployed, for example, as an electrostatic voltmeter, as the alterationin the divergence or convergence of a translated beam is a function ofthe intensity of the impressed field. The device may be employed inconnection with suitable apparatus for the transmission of audible orother signals over a beam of light. When the device is employed inconnection with transmission of audible signs it may be said to modulatethe beam of light at audible frequencies, and where such an expressionis used in the claims it should be so interpreted. It is also suited foruse in sound-recording on motion picture film.

Although the focus module of the present invention is generally drivenby what may be characterized as an electric potential, the electricalsignals or stimuli used to control the focus module may be characterizedin terms of voltages (electric potentials, or electric potentialdifferences), as well as other electrical parameters, such as electriccurrent or electric charge (the time integral of electric current). Forthe purposes of the present disclosure, the focus module, and inparticular the deforming element (as acted upon through the conductorelement), may be controlled by an applied electrical signal for drivingany type of fluid (or reconfigurable) lens that responds to the appliedsignal by exhibiting adjustable behavior based on the interaction oflight with two or more fluids (or a fluid and vacuum) having differingoptical indices.

We now describe apparatus and methods of operation that embody variousfeatures and aspects of the invention, in the form of readers having thecapability to obtain images, and to detect, analyze, and decode suchimages. In particular, the readers of the invention can in someembodiments be hand held, portable apparatus that can image encodedindicia, such as bar codes of a variety of types (1D, 2D, stacked 1D,and other bar codes), and symbols such as handwritten, printed, andtyped characters (for example using optical character recognitionmethods), as well as imaging surfaces or objects that are amenable tobeing identified using optical illumination.

FIG. 16A is a diagram showing a reader 900, such as a bar code scanner,embodying features of the invention. The reader 900 comprises variousoptical components and components of hardware and software forcontrolling the operation of the reader 900 and for analyzing an imageacquired by the reader 900. FIG. 16B is a diagram showing the controlcircuitry of the reader of FIG. 16A in greater detail. In FIG. 16A, acase 902 is shown in dotted schematic outline. The case 902 can inprinciple be any convenient enclosure or frame for supporting thevarious components in suitable mutual orientation, and in someembodiments is a case adapted to be held in a hand of a user, asdescribed in greater detail hereinbelow in conjunction with FIGS. 15 aand 15 b. The reader 900 comprises sources of illumination 904, 906 thatcan be operated in various circumstances to illuminate a target and toprovide an aiming signal. The illumination source 904 is in general asource comprising one or more light sources such as lamps or LEDs thatprovide illumination at a convenient wavelength, such as red or greenillumination, for illuminating a target whose image is to be acquired.The aimer source 906 in some embodiments is a second LED that is used toback illuminate a slit that creates an aiming signal. This slit is thenimaged onto the target 914 with an appropriate imaging optics.Alternately the aimer source (LED) 906 operates at a differentwavelength from the illumination source 904 (for example, theillumination source may be red for illumination and the aiming sourcemay be green for the aiming signal) so that it is easily distinguishedtherefrom. The aimer source 906 is used by an operator of the reader 900to ascertain what the reader is aimed at. Optics 908 are provided fordistributing the illumination from illumination source 904 in a patterncalculated to illuminate a target 914. In a preferred embodiment thetarget is illuminated optimally. In one embodiment a collimation lens910 and a diffractive element 912 are optionally provided to collimatethe light from a laser aimer source 906, and to spread or diffract thelight from the aimer source 906 in a predefined pattern, respectively.As can be seen in FIG. 16A, an object 914 to be imaged is situated on anobject plane 916 located at a distance q1 from the reader 900. Theobject 914 is for example a bar code affixed to a surface, namely theobject plane 916. For purposes of discussion, there is also shown inFIG. 16A a second object plane 916′ located at a greater distance q2from the reader 900, and having thereon an object 914′ (which can alsobe a bar code). The surface 916, 916′ is preferably illuminated, eitherby light from the illumination source 904, or by ambient light, or acombination thereof. As can be seen in FIG. 16A, the aimer 906, thecollimation lens 910 and the diffractive element 912 in combinationprovide a locator pattern 918, comprising 5 elements 918 a-918 e in FIG.16A, that identify for a user where the reader 900 is aimed, so that adesired target can be made to fall within the aiming area of the reader900. Light reflected from the target (or alternatively, light generatedat the target) is captured by the reader using a lens 920, which in someembodiments comprises a fluid lens and possibly one or more fixedlenses, and is conveyed via the fluid lens to an imager 922. The imager922 in various embodiments is a 1D or 2D semiconductor array sensor,constructed using any convenient processing technology, such as a CMOSsensor, a CCD sensor, or the like. The imager 922 converts the opticalsignals that it receives into electrical signals that representindividual pixels of the total image, or frame, or a portion thereof. Invarious embodiments, the imager can be any of a color CCD imager, and acolor CMOS imager.

The reader 900 also includes various hardware components, shown in asingle control element 930 for controlling and for acquiring signalsfrom the reader 900 in FIG. 16A. The details of control element 930 areshown in FIG. 16B. An illumination control 931 is provided to controlthe intensity and timing of illumination provided by the illuminationsource 904. The illumination control 931 is in electrical communicationwith illumination source 904 by way of a cable 905 comprisingconductors. An aimer control 932 is provided to control the intensity,color and timing of illumination provided by the aimer source 906. Theaimer control 932 is in electrical communication with aimer source 906by way of a cable 907 comprising conductors. An imager control 934 isprovided to control the timing and operation of the imager 922, forexample by providing clocking signals to operate the image, resetsignals, start and stop signals for capturing illumination, andsynchronization signals for providing electrical output as dataindicative of the intensity of illumination received at any pixel of theimager array 922, which data may be provided as analog or as digitaldata. The imager control 934 is in electrical communication with imager922 by way of a cable 923 comprising conductors. A lens controller 938is provided to control the behavior of the fluid lens 920. The lenscontroller 938 and the fluid lens 920 are in electrical communication byway of a cable 921 comprising conductors.

An analog-to-digital converter 936 is provided for converting analogsignals output by the imager 922 to digital signals. In someembodiments, a DMA controller 948 is provided to allow direct transferof digital data to a memory for storage. In general, any and all ofillumination control 931, aimer control 932, imager control 934, A/D 936and DMA 948 are connected to a general purpose programmable computer 942by way of one or more buses 945, which buses 945 may be serial buses orparallel buses as is considered most convenient and advantageous. Thegeneral purpose programmable computer 942 comprises the usualcomponents, including a CPU 943 which can in some embodiments be amicroprocessor, and memory 944 (for example semiconductor memory such asRAM, ROM, magnetic memory such as disks, or optical memory such asCD-ROM). The general purpose computer can also communicate via one ormore buses 947 with a wide variety of input and output devices. Forexample, there can be provided any or all of an output device 946 suchas a display, a speaker 948 or other enunciator, devices for inputtingcommands or data to the computer such as a keyboard 950, a touchpad 952,a microphone 954, and bidirectional devices such as one or more I/Oports 956 which can be hardwired (i.e., serial, parallel, USB, firewireand the like) or can be wireless (i.e., radio, WiFi, infra-red, and thelike). The general purpose programmable computer 942 can also comprise,or can control, indicators 960 such as LEDs for indicating status orother information to a user.

As shown in FIG. 16A, the reader 900 and/or the general purpose computer942 (as shown in FIG. 16B) can comprise one or more trigger switches 964that allow a user to indicate a command or a status to the reader 900.In addition, the entire system is provided with electrical power by theuse of one or more of a power supply 970, batteries 972 and a charger974. Any convenient source of electrical power that can be used tooperate the reader 900 and its associated general purpose programmablecomputer 942 (as shown in FIG. 16B) is contemplated, including theconventional electrical grid (which can be accessed by connection to aconventional wall plug), and alternative power sources such as emergencygenerators, solar cells, wind turbines, hydroelectric power, and thelike.

A laser bar code scanner can be implemented with a steering lensconfiguration. See FIGS. 38A-38C hereinbelow. Rather than using ascanning mirror or motor as presently used in bar code scanners, thescanning motion can be achieved with a steerable fluid lens. At the sametime the laser spot location of narrowest beam width can also beeffected with the same or a different fluid lens. Such a scanning systemcan also be coaxial in nature, where the receive and transmit lightbeams both focus at the same section of the bar code pattern beingscanned. This receive optical system is not shown, but these are wellknown to those in the art. A cylindrical or spherical scanning fluidlens may be used depending upon if the designer wishes to develop asingle scan line or a raster scan line. It is also envisioned that itmay be possible to develop a fluid element that scans only, withouthaving optical power. Such systems are also contemplated.

As may be seen from FIG. 16A, the distance at which the reader of theinvention can operate, or equivalently, a focal length of the opticalsystem of the reader, can vary as the distance q from the lens to theobject to be imaged varies. The focal length for a specific geometricalsituation can be determined from the formula1/f=1/p+1/qin which f is the focal length of a lens, p is the distance from thelens to a surface at which a desired image is observed (such as animaging sensor or a photographic film), and q is a distance between thelens and the object being observed.

Consider the two objects situated at a nearer distance q1 and a fartherdistance q2 from the reader lens (e.g., q2>q1). In a system that is lessexpensive and more convenient to construct, the distance p (from thelens 920 to the imaging sensor 922) is fixed. One can image objectslying at the distance q1 from the lens with a focal length given by1/f1=1/p+1/q1, and one can image objects lying at the distance q2 fromthe lens with a focal length given by 1/f2=1/p+1/q2. Since q2>q1, and pis constant, we have f1<f2. In particular, for a reader comprising afluid lens that can provide a minimum focal length of f1 and a maximumfocal length of f2, for a fixed value of p, one would have the abilityto observe in proper focus objects at distances ranging at least from q1to q2, without consideration for issues such as depth of field at aparticular focal length setting of the lens. By way of example, q1 mightbe a short distance such as 4 inches (approximately 10 cm) so that onecan image a target object having much detail (such as a high density barcode) with recovery or decoding of all of the detail present in theobject. On the other hand, q2 might be a longer distance, such as 12inches (approximately 30 cm) or more, whereby a reader can image anobject at longer distance with lesser density (e.g., fewer pixels ofresolution per unit of length or area observed at the target object).Accordingly, a reader of the invention comprising a particular imagingsensor can be configured to perform at either extreme of highdensity/short distance or of low density/long distance (or any variantintermediate to the two limits) by the simple expedient of controllingthe focal length of the fluid lens such that an object at the intendeddistance d in the range q2≧d≧q1 will be imaged correctly.

The lens can be caused to either manually or automatically change itsfocal length until the best focus is achieved for an object at a givendistance away. One way to do this is to minimize the so-called blurcircle made by a point or object within the field of view. This can bedone automatically by a microprocessor that varies the focal length ofthe lens and measures the size of the blur circle on a CCD or CMOSimager; i.e. the number of pixels the blur circle fills. The focallength at which the blur circle is smallest is the best focus and thelens is held at that position. If something in the field of viewchanges, e.g. the object gets farther away from the lens, then themicroprocessor would detect the change and size of the blur circle andreinitiate the automatic focusing procedure.

The object used to measure the blur circle could be a detail inherentlyin the field of view, or it could be a superimposed object in the fieldof view. As an example, one could project an IR laser spot into thefield (the wavelength of the IR is beyond the sensitivity of the humaneye, but not of the CCD or CMOS image sensor). Another means ofachieving best focus includes transforming the image into the frequencydomain, for example with a Fourier transform, and then adjusting thefocal length of the fluid lens to maximize the resulting high frequencycomponents of that transformed image. Wavelet transforms of the imagecan be used in a similar fashion. Both the frequency domain and wavelettechniques are simply techniques for achieving best focus viamaximization of contrast among the pixels of the CCD or CMOS imagesensor. These and similar procedures, such as maximizing the intensitydifference between adjacent pixels, are known in the art and arecommonly used for passive focusing of digital cameras.

FIG. 17 is a block diagram of an optical reader showing a generalpurpose microprocessor system that is useful with various embodiments ofthe invention. Optical reader 1010 includes an illumination assembly1020 for illuminating a target object T, such as a 1D or 2D bar codesymbol, and an imaging assembly 1030 for receiving an image of object Tand generating an electrical output signal indicative of the dataoptically encoded therein. Illumination assembly 1020 may, for example,include an illumination source assembly 1022, together with anilluminating optics assembly 1024, such as one or more lenses,diffusers, wedges, reflectors or a combination of such elements, fordirecting light from light source 1022 in the direction of a targetobject T. Illumination assembly 1020 may comprise, for example, laser orlight emitting diodes (LEDs) such as white LEDs or red LEDs.Illumination assembly 1020 may include target illumination and opticsfor projecting an aiming pattern 1027 on target T. Illumination assembly1020 may be eliminated if ambient light levels are certain to be highenough to allow high quality images of object T to be taken. Imagingassembly 1030 may include an image sensor 1032, such as a 1D or 2D CCD,CMOS, NMOS, PMOS, CID OR CMD solid state image sensor, together with animaging optics assembly 1034 for receiving and focusing an image ofobject T onto image sensor 1032.

The array-based imaging assembly shown in FIG. 17 may be replaced by alaser array based scanning assembly comprising at least one lasersource, a scanning mechanism, emit and receive optics, at least onephotodetector and accompanying signal processing circuitry. See FIGS.38A, 38B, and 38C hereinbelow, and the associated description.

A partial frame clock out mode is readily implemented utilizing an imagesensor which can be commanded by a control module to clock out partialframes of image data or which is configured with pixels that can beindividually addressed. Using CMOS fabrication techniques, image sensorsare readily made so that electrical signals corresponding to certainpixels of a sensor can be selectively clocked out without clocking outelectrical signals corresponding to remaining pixels of the sensor,thereby allowing analysis of only a partial frame of data associatedwith only a portion of the full imager field of view. CMOS image sensorsare available from such manufacturers as Symagery, Omni Vision, Sharp,Micron, STMicroelectronics, Kodak, Toshiba, and Mitsubishi. A partialframe clock out mode can also be carried out by selectively activating aframe discharge signal during the course of clocking out a frame ofimage data from a CCD image sensor. A/D 1036 and signal processor 1035may individually or both optionally be integrated with the image sensor1032 onto a single substrate.

Optical reader 1010 of FIG. 17 also includes programmable controlcircuit (or control module) 1040 which preferably comprises anintegrated circuit microprocessor 1042 and an application specificintegrated circuit (ASIC 1044). The function of ASIC 1044 could also beprovided by a field programmable gate array (FPGA). Processor 1042 andASIC 1044 are both programmable control devices which are able toreceive, to output and to process data in accordance with a storedprogram stored in memory unit 1045 which may comprise such memoryelements as a read/write random access memory or RAM 1046 and anerasable read only memory or EROM 1047. Other memory units that can beused include EPROMs and EEPROMs. RAM 1046 typically includes at leastone volatile memory device but may include one or more long termnon-volatile memory devices. Processor 1042 and ASIC 1044 are also bothconnected to a common bus 1048 through which program data and workingdata, including address data, may be received and transmitted in eitherdirection to any circuitry that is also connected thereto. Processor1042 and ASIC 1044 differ from one another, however, in how they aremade and how they are used. The processing module that is configured toextract information encoded by the encoded indicium employs some or allof the capabilities of processor 1042 and ASIC 1044, and comprises thehardware and as necessary, software and or firmware, required toaccomplish the extraction task, including as necessary decoding tasks toconvert the raw data of the image to the information encoded in theencoded indicium.

More particularly, processor 1042 is preferably a general purpose,off-the-shelf VLSI integrated circuit microprocessor which has overallcontrol of the circuitry of FIG. 17, but which devotes most of its timeto decoding image data stored in RAM 1046 in accordance with programdata stored in EROM 1047. ASIC 1044, on the other hand, is preferably aspecial purpose VLSI integrated circuit, such as a programmable logicarray or gate array that is programmed to devote its time to functionsother than decoding image data, and thereby relieves processor 1042 fromthe burden of performing these functions.

The actual division of labor between processors 1042 and 1044 willnaturally depend on the type of off-the-shelf microprocessors that areavailable, the type of image sensor which is used, the rate at whichimage data is output by imaging assembly 1030, etc. There is nothing inprinciple, however, that requires that any particular division of laborbe made between processors 1042 and 1044, or even that such a divisionbe made at all. This is because special purpose processor 1044 may beeliminated entirely if general purpose processor 1042 is fast enough andpowerful enough to perform all of the functions contemplated by thepresent invention. It will, therefore, be understood that neither thenumber of processors used, nor the division of labor there between, isof any fundamental significance for purposes of the present invention.

With processor architectures of the type shown in FIG. 17, a typicaldivision of labor between processors 1042 and 1044 will be as follows.Processor 1042 is preferably devoted primarily to such tasks as decodingimage data, once such data has been stored in RAM 1046, recognizingcharacters represented in stored image data according to an opticalcharacter recognition (OCR) scheme, handling menuing options andreprogramming functions, processing commands and data received fromcontrol/data input unit 1039 which may comprise such elements as atrigger 1074 and a keyboard 1078 and providing overall system levelcoordination.

Processor 1044 is preferably devoted primarily to controlling the imageacquisition process, the A/D conversion process and the storage of imagedata, including the ability to access memories 1046 and 1047 via a DMAchannel. The A/D conversion process can include converting analogsignals to digital signals represented as 8-bit (or gray scale)quantities. As A/D converter technology improves, digital signals may berepresented using more than 8 bits. Processor 1044 may also perform manytiming and communication operations. Processor 1044 may, for example,control the illumination of LEDs 1022, the timing of image sensor 1032and an analog-to-digital (A/D) converter 1036, the transmission andreception of data to and from a processor external to reader 1010,through an RS-232, a network such as an Ethernet or other packet-basedcommunication technology, a serial bus such as USB, and/or a wirelesscommunication link (or other) compatible I/O interface 1037. Processor1044 may also control the outputting of user perceptible data via anoutput device 1038, such as a beeper, a good read LED and/or a displaymonitor which may be provided by a liquid crystal display such asdisplay 1082. Control of output, display and I/O functions may also beshared between processors 1042 and 1044, as suggested by bus driver I/Oand output/display devices 1037′ and 1038 or may be duplicated, assuggested by microprocessor serial I/O ports 1042A and 1042B and I/O anddisplay devices 1037″ and 1038′. As explained earlier, the specifics ofthis division of labor is of no significance to the present invention.

FIG. 18 is a flow chart 1100 showing a process for operating a systemhaving an adjustable focus system comprising feedback, for example asystem having components as described in FIG. 16A. The process begins atstep 1110, where a command to capture an image is generated, for exampleby a user depressing a trigger, or by an automated system issuing acapture image command in response to a specified condition, such as anobject being sensed as coming into position for imaging. Once an imageis captured at step 1110, the image focus is assessed, as indicated atstep 1120. Focus assessment can comprise comparison of the image qualitywith a specified standard or condition, such as the sharpness ofcontrast at a perceived edge of a feature in the image, or otherstandards.

Another procedure for performing an autofocus operation using a flatnessmetric includes the following steps:

1. capturing a gray scale image (i.e., capture an image with the handheld reader and digitize the image using at least two bit resolution, orat least 4 discrete values);

2. optionally sampling the gray scale image (i.e., extract from theimage a line or a series of points, or alternatively, the sampled imagecan be the captured image if it is a windowed frame comprising imagedata corresponding to selectively addressed pixels);

3. creating a histogram by plotting number of occurrences of data pointshaving a particular gray scale value, for example using the X axis torepresent gray scale values and the Y axis to represent frequency ofoccurrence;

4. processing the histogram to provide a flatness measurement as output;

5. determining a focus level (or quality of focus) based on the flatnessmeasurement; and

6. in the event that the quality of focus as determined from theflatness metric is less than desired, changing the focus and repeatingsteps 1 through 5.

The flatness of an image refers to the uniformity of the distribution ofdifferent gray scale values in the histogram. A flat distribution is onewith little variation in numbers of observations at different gray scalevalues. In general, poorly focused images will be “flatter” than betterfocused images, i.e. there will be a relatively even incidence of grayscale values over the range of gray scale values. Generally, a histogramfor a well focused image has many pixels with high gray scale values,many pixels with low gray scale values, and few pixels in the middle.The use of historical information for various types of images, such asbar codes, including information encoded in look up tables, orinformation provided using the principles of fuzzy logic, iscontemplated

At step 1130, the outcome of the focus assessment is compared to anacceptable criterion, such as sharpness (or contrast change) of aspecified amount over a specified number of pixels. Images that aredigitized to higher digital resolutions (e.g., using a range defined bya larger number of bits) may support more precise determinations ofacceptable focus. If the result of the assessment of focus is negative,the process proceeds to step 1140, where the focus of the lens 920 ofFIG. 16A, is modified. After adjusting the focus, the operation of theprocess returns to step 1110, and a new image is captured, and isassessed. When an image is captured that is found to have suitablefocus, the process moves from step 1130 to step 1150, wherein the imagewith suitable focal properties is processed, and a result is madeavailable to a user or to the instrumentality that commanded thecapturing of the image, and/or the result is stored in a memory.Optionally, as indicated at step 1160, the system can be commanded toobtain another image, that is to loop back to the step 1110, and torepeat the process again.

FIG. 19 is a flow chart showing a process for operating a system havingan adjustable focus system that does not comprise feedback. At step 1210a command to capture an image is generated, for example by a userdepressing a trigger, or by an automated system issuing a capture imagecommand in response to a specified condition, such as an object beingsensed as coming into position for imaging. At step 1215, the lens 920is driven with a first fluid lens control signal corresponding to afirst condition, such as a default condition, for example using avoltage applied to the lens 920 that causes the lens 920 to operate byapproximation with focal position q1 of 7 inches. In a preferredembodiment, the applied voltage to focus at 7 inches is zero appliedvolts. Using this focal condition, an image is captured and processed atstep 1220. At step 1225, the information retrieved from the capturedimage is examined to determine if a valid decoding of a bar code hasbeen achieved. If the decoding is valid, the information or datarepresented by the decoded image is reported as indicated at step 1260,and the process stops, as indicated at step 1270. A later command torepeat the process can be given as may be necessary or advantageous.

If at step 1225 it is determined that a good decode has not beenachieved, the process continues to step 1230, at which time the fluidlens control signal applied to the lens 920 is adjusted to a firstalternative value, for example a voltage that causes the lens 920 tofocus by approximation at a distance q2 of 30 cm. Using this focalcondition, an image is captured and processed at step 1235. At step1240, the information retrieved from the captured image is examined todetermine if a valid decoding of a bar code has been achieved. If thedecoding is valid, the information or data represented by the decodedimage is reported as indicated at step 1260, and the process stops, asindicated at step 1270.

If at step 1240 it is determined that a good decode has not beenachieved, the process continues to step 1245, at which time the fluidlens control signal applied to the lens 920 is adjusted to a secondalternative value, for example a voltage that causes the lens 920 tofocus by approximation at a distance q3 of 100 cm. Using this focalcondition, an image is captured and processed at step 1250. At step1255, the information retrieved from the captured image is examined todetermine if a valid decoding of a bar code has been achieved. If thedecoding is valid, the information or data represented by the decodedimage is reported as indicated at step 1260, and the process stops, asindicated at step 1270. If a valid decoding of a bar code is still notachieved, the process returns to step 1215, and the process is repeatedto try to identify a valid bar code value. In other embodiments, after aspecified or predetermined number of iterative loops have occurredwithout a successful outcome, or after a specified or predetermined timeelapses, the process can be aborted by a supervisory control device,which in some embodiments can operate according to a computer program.Alternately the process may stop if the trigger is released. Althoughthe process depicted in FIG. 19 uses three discrete conditions to drivethe lens 920 in the search for a suitable focus condition, it ispossible to use more or fewer than three predefined drive conditions ascomponents of such a process. For example, one can define a process inwhich the focal distance changes by a predefined distance, or apredefined percentage. Alternatively, one can define a process in whichthe adjustment is based upon a quantity determined from the informationobtained in assessing whether the captured image is in focus (asdescribed hereinabove) or from the quality of the decoded information(e.g., whether the information is completely garbled or incorrectlyformatted, or is close to being valid). In general, the distancesspecified may not be attained to absolute precision (for example, adistance of 30 cm may not be measured to a precision of 30.000 cm butmerely to 30 cm to within one tenth of a centimeter), but rather thetest is that the lens operates adequately at the distance that isidentified. In the laboratory, precise distances may be set up forexperiments, but in actual use in the field, distances are measured lessaccurately than in the laboratory.

Fluid lenses may have aberrations, such as spherical aberration and/orcolor aberration. In the focus module of the invention, additionallenses, such as positive or negative lenses, can be used in conjunctionwith the focus module such as lens 920 to correct one or more ofspherical, color, or higher order aberrations. In some embodiments, thematerials of construction of the additional lenses can be chosen so asto compensate for optical imperfections and aberrations introduced bythe fluid lens.

FIGS. 22 a and 22 b are drawings of hand held readers that embodyfeatures of the invention. FIG. 22 a shows a hand held reader 1500comprising a case having a substantially linear shape. The handheldreader 1500 comprises circuitry as has been described with regard toFIG. 17, including data processing capability and memory. The hand heldreader 1500 comprises an input device 1510, such as a key pad, for useby a user, one or more buttons of which may also be used as a trigger1534 to allow a user to provide a trigger signal. The hand held reader1500 comprises an output device 1512, such as a display, for providinginformation to a user. In some embodiments, the display 1512 comprises atouch screen to allow a user to respond to prompts that are displayed onthe display 1512, or to input information or commands using any of iconsor graphical symbols, a simulated keypad or keyboard, or throughrecognition of handwritten information. Hand held reader 1500 can alsocomprise a touch pad or touch screen that can display information as anoutput and accept information as an input, for example displaying one ormore icons to a user, and accepting activation of one of the icons bythe user touching the touch pad or touch screen with a finger or with astylus 1508. The hand held reader 1500 also comprises a bar code imageengine 1514 that includes a fluid lens. The image engine 1514 acquiresimages of objects of interest that the hand held reader 1500 is employedto read. The fluid lens provides the ability to adjust a focal distanceand to adjust an optical axis of the image engine 1514, as is describedin more detail herein. The hand held reader 1500 also comprises a cardreader 1520 that is configured in various embodiments to read cardsbearing information encoded on a magnetic strip, such as is found oncredit cards, and information encoded in a semiconductor memory, such asfound in PC, PCMCIA or smart cards. The hand held reader 1500 alsocomprises a wireless communication device 1530 such as a radiotransceiver and/or an infrared transceiver for communication with aremote base station, a computer-based data processing system, a secondhand held reader 1500′, or a device such as a PDA. The hand held reader1500 also comprises an RFID transceiver 1532 for communicating with anRFID tag. As used herein, the term “RFID tag” is intended to denote aradio-frequency identification tag, whether active or passive, andwhether operating according to a standard communication protocol or aproprietary communication protocol. An RFID transceiver can beprogrammed to operate according to a wide variety of communicationprotocols. FIG. 22 a also depicts a card 1540 that in differentembodiments includes information encoded on at least one of a magneticstripe, a semiconductor memory, smart card, and in RFID tag. An exampleof a hand held reader 1500 in which such fluid lens systems can beemployed is the PDT 9500, available from HandHeld Products, Inc. ofSkaneateles Falls, N.Y. In one embodiment, the CMOS image array can beimplemented with a Micron image sensor such as the Wide VGA MT9V022image sensor from Micron Technology, Inc., 8000 South Federal Way, PostOffice Box 6, Boise, Id. 83707-0006. The MT9V022 image sensor with fullframe shutter is described in more detail in the product MT9V099 productflyer available from Micron Technology (www.micron.com), for example athttp://download.micron.com/pdf/flyers/mt9v022_(mi-0350)_flyer.pdf. TheICM105T CMOS progressive imager available from IC Media, 5201 GreatAmerica Pkwy, Suite 422, Santa Clara, Calif. 95054 might also be used.The imager is shown at websitehttp://www.ic-media.com/products/view.cfm?product=ICM%2D105T. Thisimager uses a rolling shutter. Although both imagers cited areprogressive imagers, as is well known in the art, interleaved imagerswill also function properly in these systems.

FIG. 22 b shows another embodiment of a hand held reader 1550 whichcomprises components as enumerated with respect to hand held reader1500, including specifically input 1510, output 1512, image engine andfluid lens 1514, card reader 1520, radio 1530, and RFID transceiver1532. The handheld reader 1550 comprises circuitry as has been describedwith regard to FIG. 17, including data processing capability and memory.For hand held reader 1550, the case 1560 comprises a “pistol grip” or aportion disposed at an angle, generally approaching 90 degrees, to anoptical axis of the imaging engine and fluid lens of the reader 1550.Hand held reader 1550 also comprises a trigger 1534, for examplesituated on the pistol grip portion of the reader 1550, and located soas to be conveniently operated by a finger of a user. Hand held reader1550 also comprises a cable or cord 1570 for connection by wire to abase station, a computer-based data processing system, or a point ofsale apparatus. Alternately reader 1550 may communicated to a basestation by means of an internal radio (not shown). Examples of readers1550 in which such fluid lens systems can be employed are the IT 4600comprising a 2D image sensor array, and the IT 5600 comprising a 1Dimage sensor array, all available from HandHeld Products, Inc. ofSkaneateles Falls, N.Y.

In some embodiments, the hand held readers 1500 and 1550 are deployed ata fixed location, for example by being removably secured in a mounthaving an orientation that is controlled, which may be a stationarymount or a mount that can be reoriented. Examples of such uses are in acommercial setting, for example at a point of sale, at the entrance orexit to a building such as an office building or a warehouse, or in agovernment building such as a school or a courthouse. The hand heldreaders of the invention can be used to identify any object that bearsan identifier comprising one or more of a bar code, a magnetic stripe,an RFID tag, and a semiconductor memory.

In some embodiments, the hand held reader 1500, 1550 can be configuredto operate in either a “decode mode” or a “picture taking” mode. Thehand held reader 1500, 1550 can be configured so that the decode modeand picture taking mode are user-selectable. For example, the reader canbe configured to include a graphical user interface (GUI) for example ona touch pad or key pad that is both an input and an output device asdepicted in FIGS. 22 a and 22 b enabling a user to select between thedecode mode and the picture taking mode. In one embodiment, the decodemode is selected by clicking on an icon displayed on a display such asdisplay 1512 of FIG. 22 a whereby the reader is configured with a decodemode as a default. Alternatively, the mode of operation (either “decodemode” or “picture taking mode”) can be set by a communication from aremote device, or by default upon initial activation of the reader, aspart of a power-up sequence. Thus, the reader is configured to operatein the decode mode on the next (and subsequent) activation of trigger1534 to generate a trigger signal. In the decode mode, the hand heldreader 1500, 1550 in response to the generation of the trigger signalcaptures an image, decodes the image utilizing one or more bar codedecoding algorithms and outputs a decoded out message. The decoded outmessage may be output, e.g., to one or more of a memory, a display 1512or to a remote device, for example by radio communication or by ahardwired communication.

In one embodiment, the “picture taking mode” is selected is selected byclicking on icon (which can be a toggle switch). Alternately hand heldreader 1500, 1550 is configured in a “picture taking mode” as thedefault mode. Thus, the hand held reader 1500, 1550 is configured tooperate in the “picture taking mode” on the next (and subsequent)activation of trigger 1534 to generate a trigger signal. The hand heldreader 1500, 1550 in response to the generation of the trigger signalcaptures an image and outputs an image to one or more of a memory, to adisplay 1512, or to a remote device.

The hand held reader 1500, 1550 can be configured so that when the imagecapture mode is selected, the hand held reader 1500, 1550 avoidsattempting to decode captured images. It is understood that in theprocess of capturing an image for decoding responsively to receipt of atrigger signal, the hand held reader 1500, 1550 may capture a pluralityof “test” frames, these may be full frames or only partial frames asdiscussed above, for use in establishing imaging parameters (e.g.,exposure, gain, focus, zoom) and may discard frames determined afterdecode attempts to not contain decodable symbol representations.Likewise in the process of capturing an image for image outputresponsively to receipt of a trigger signal in a picture taking mode,the hand held reader 1500, 1550 may capture test frames, these may befull frames or only partial frames as discussed above, for use inestablishing imaging parameters and may also discard images that aredetermined to be unsuitable for output. It is also understood that inthe “picture taking mode” the images captured may be archived for lateranalysis, including decoding of bar codes or other encoded indicia thatmay be present in the images, for example for use in providing evidenceof the condition of a package at the time of shipment from a vendor forinsurance purposes (which image may never be decoded if the packagearrives safely). Other examples of similar kind can be a photograph of aloaded truck, for example with a license plate, an identifying number orsimilar indication of which of many possible trucks is the subject ofthe photograph, optionally including a date and time, and possibly otherinformation that can be stored with the image, such as the identity ofthe photographer (e.g., a name, an employee number, or other personalidentifier).

In an alternative embodiment, the hand held reader 1500, 1550 displays aplurality of icons (at least one for decode mode and one for picturetaking mode) whereby activation of an icon both configures the hand heldreader 1500, 1550 to operate in the selected operating mode (decoding orpicture taking) and results in a trigger signal automatically beinggenerated to commence an image capture/decode (decode mode) or imagecapture/output image process (picture taking mode). Thus, in thealternative embodiment, the trigger 1534 need not be actuated tocommence image capture after an icon is actuated.

FIG. 23 is a diagram 1600 of a handheld reader of the invention incommunication with a computer. In FIG. 23, a hand held reader 1550 ofthe type described hereinabove is connected by way of a cable 1570 to acomputer 1610, which in the embodiment depicted is a laptop or portablecomputer. The computer 1610 comprises the customary computer components,including an input 1612, which may include a keyboard, a keypad and apointing device such as a mouse 1608, an output 1614 for use by a user,such as a display screen, and software 1630 recorded on one or moremachine-readable media. Examples of software that operate on thecomputer 1610 are a program 1632 that provides a quick view of the imageas “seen” by the image engine and fluids lens in the hand held reader1550 on the display 1614 of the computer 1610, and a interactive program1634, for example provided on a machine readable medium, (not shown)that allows a user to control the signal (such as a voltage or electricpotential) applied to the fluid lens and to observe that response of thefluid lens thereto, for example as a representation in a graph or as arepresentation of one or more images read by the reader as the fluidlens control signal is varied. In FIG. 23, there are also shown aplurality of test targets 1620, 1622, 1624, which in some embodimentsare optical test targets conforming to a test target known as the UnitedStates Air Force (“USAF”) 1951 Target (or 1951 USAF Resolution Target)as shown and described at the web sitehttp://www.sinepatterns.com/USAF_labels.htm, and provided commerciallyin a variety of forms by SINE PATTERNS LLC, 1653 East Main Street,Rochester, N.Y. 14609, a manufacturer of the 1951 USAF Target and manyother types of targets and visual patterns, as further indicated at theweb site http://www.sinepatterns.com/i_Stdrds.htm.

The example depicted in FIG. 23 shows a target at each of threedistances or positions relative to the hand held reader 1550. In oneembodiment, the three targets lie along a single optical axis atdiscrete, different distances. In another embodiment, the three targets1620, 1622, 1624 lie at the same distance along distinct optical axesrelative to hand held reader 1550. In some embodiments, both thedistances between the hand held reader 1550 and the targets aredistinct, and the optical axes from the hand held reader 1550 to thetargets are also distinct. Each target 1620, 1622, 1624 presents anobject, such as a known test pattern of defined geometry, that the handheld reader 1550 can image. By controlling the behavior of the fluidlens in the hand held reader 1550, it is possible to calibrate theoperation of the fluid lens by recording the observed control signal(such as a voltage or impressed electric potential) that is required toobtain an acceptable (e.g., an image within an acceptable range of imagequality or one that can be correctly decoded to retrieve informationencoded therein), and preferably optimal, image of the target at eachlocation or position.

FIG. 24 is a flow chart 1700 of a calibration process useful forcalibrating an apparatus embodying features of the invention. In FIG.24, the calibration is initiated, as shown at step 1705, by initializingthe system, including performing all power-on-sequence tests to assurethat the system components are operating properly. At step 1710, a testtarget bearing a pattern or encoded symbol is positioned at a first testposition. When in the first test position, the target will in general beat defined distance and orientation relative to the hand held readercomprising a fluid lens. At step 1715, the fluid lens control signal(which in some embodiments is a voltage) is adjusted to obtain anacceptable, and preferably an optimal, focus condition for the target.At step 1720, the distance and orientation of the target and the fluidlens control signal parameters (for example magnitudes and signs ofvoltages, timing features of the signal such as pulse duration,transition time and repetition rate) are recorded for future use in anon-volatile memory, for example in a table.

One can iteratively repeat the process steps of locating the target at anew location and orientation, controlling the fluid lens control signalapplied to the fluid lens to obtain a satisfactory, and preferablyoptimal, focus, and recording in a memory the information about thetarget location and orientation and the fluid lens control signalparameters, so as to provide a more complete and detailed set ofcalibration parameters. The number of iterations is limited only by theamount of time and effort one wishes to expend performing calibrationsteps, and the amount of memory available for recording the calibrationparameters observed. In the example presented in FIG. 23, a calibrationaccording to the flow diagram of FIG. 24 would include performingcalibration steps as described by steps 1710, 1715 and 1720 at threedistinct positions for the target. The information obtained incalibration tests can be used when operating the corresponding imager(or in some instances, another imager of similar type) either by usingthe calibration information as an initial setting for operation in aclosed loop mode as explained in connection with FIG. 18, or as fixedoperating conditions for discrete points in an open loop operating modeas explained in connection with FIG. 19.

FIG. 25 is a diagram 1800 showing calibration curves for a plurality ofexemplary hand held readers. In FIG. 25, the horizontal axis 1802represents a fluid lens control signal parameter, such as voltage, andthe vertical axis 1804 represents an optical property of the fluid lens,such as optical power. One can also represent other optical propertiesof a fluid lens that are relevant for its operation, such as focallength, f-number, and deviation from a default optical axis (whichdefault optical axis may be considered to represent zero degrees ofelevation or altitude and zero degrees of azimuth). In FIG. 25, threecurves 1810, 1812, 1814 are shown, each curve representing a response(e.g., optical power) of a specific fluid lens to an applied fluid lenscontrol signal (e.g., voltage). As seen in FIG. 25, the curve 1810,representing the behavior of a first fluid lens, reaches an opticalpower P 1820 at an applied voltage V1 1830. However, other fluid lensesmay behave slightly differently, such that a second fluid lens,represented by curve 1812, attains optical power P at an somewhat largervoltage V2 1832, and a third fluid lens, represented by curve 1814,attains optical power P at yet a larger voltage V3 1834. Accordingly,one can extract from the information in FIG. 25 a relation between thefluid lens control signal that is to be applied to the first fluid lensand the second fluid lens to attain the same optical power P, forexample for operating two hand held readers under substantially similarconditions, or for operating a binocular reader or other device thatuses two fluid lenses simultaneously, for example to generate astereoscopic view of a target. At power P, there exists a difference indrive voltage between the first lens and the second lens given by V2-V1,where the difference has a magnitude given by the absolute value ofV2-V1 and a sign which is positive if V2 exceeds V1 in magnitude,negative if V1 exceeds V2 in magnitude, and zero if V2=V1. In operation,in order to attain optical power P in both of the first and second fluidlenses, one can provide a fluid lens control signal equal to V1 to boththe first and second fluid lenses, and a differential signal equal tothe signed difference of V2-V1 to the second fluid lens. Alternatively,one could use two power supplies that provide signals V1 and V2 to thefirst and second fluid lenses, respectively. As the optical powerrequired for operation of a fluid lens changes, the fluid lens controlsignal changes, and can be deduced or read from the appropriate curve ofFIG. 25. Since one in general does not measure the parameters of a fluidlens or other device at all possible values within a range, a curve suchas 1810 can also be obtained by measuring a discrete number of pairs ofoptical parameter and associated fluid lens control signal, and fittinga curve to the data, or interpolating values between adjacent datapoints, as may be most convenient to prepare a suitable calibrationcurve. In some instances, only a single calibration point per fluid lensmodule may be required. Rather than creating curves for different fluidlenses, one can measure the same fluid lens at different temperatures.Then the appropriate operating point can be determined at the varioustemperatures. Other operating points may be determined by eitherextrapolation or interpolation, by suitable curve fitting relationships,or by deducing a representation of the behavior in the form of anequation.

FIG. 26 is a diagram showing an embodiment of a power supply 1900suitable for use with hand held readers. In general, the first orderelectrical equivalent circuit for a fluid lens is a simple capacitor. InFIG. 26, a load 1910 represents in one embodiment a capacitive load to apower supply, generally 1920. Because the load is capacitive, the netpower consumed is in general small. The power supply 1920 of FIG. 26 isone possible embodiment, which is described first at a high level. Theoutput of this power supply can be used as input to the commutator shownin FIG. 20 comprising switches 1310, 1312, 1314, and 1316. A powersource, such as a 6 volt battery 1922, is adequate for operation of thesupply. The voltage of the power source may be increased using aDC-to-DC converter comprising a switcher IC 1930 having a sensingterminal, a controller for a switch 1940, (such as a transistor) and aninductor 1935 (which may be provided externally to the switcher). Thesense terminal in some embodiments is connected to a voltage divider1955. A rectifier 1945 is used to provide a unipolar output, whichincludes noise introduced by the switching operation of the switcher.The output voltage of the first stage of the power supply can becontrolled, and in general will be of the order of tens of volts, forexample 60 V DC. A filter 1960, such as a low pass RC filter, isprovided to eliminate noise, as the capacitive elements represent asmall impedance as frequency is increased, and represent a large(substantially infinite) impedance to low frequencies. A precision lownoise series regulator 1970 is used to control the output voltage forexample by controlling a transistor 1972, with a sense input to theseries regulator providing a feedback loop through voltage divider 1975.A control 1984 is provided to permit adjustment of the voltage signalapplied to the fluid lens, and thereby providing control of a focaldistance or plane of focus of the fluid lens 1910. Alternative powersupplies that can provide a unipolar output can be used. By using a pairof power supplies (e.g., one providing a positive voltage and oneproviding a negative voltage), a single power supply and a suitablybiased inverter, or by using a single power supply and dual operationalamplifiers, one can provide a pair of outputs that are symmetricrelative to ground.

FIGS. 28 a-28 c are cross-sectional drawings showing an exemplary fluidlens 2100 with a mount comprising an elastomer for a hand held reader.Such elastomers are made by Chomerics North America, Parker HannifinCorp., 77 Dragon Court, Woburn, Mass. 01801. In FIG. 28 a, a fluid lens2110 is shown with a solid body 2112 in the form of a ring, andelectrical contacts 2114, 2116 disposed on opposite sides thereof. Insome embodiments, the fluid lens body 2112 is made of metal, and canalso represent one of the contacts 2114, 2116, the other contact beinginsulated from the metal body 2112. In other embodiments, the body 2112is made from, or comprises, a non-conducting substance.

In FIG. 28 b, the fluid lens body 2112 is shown mounted in a holder2120. In one embodiment, the holder 2120 is tubular and has aninternally threaded surface 2130 and a partially closed end 2132 havingdefined therein an aperture of sufficient size not to occlude theoptically active portion of the fluid lens. The fluid lens body 2112 isheld in place by a threaded retainer ring 2122 that threadedly mateswith the internally threaded surface 2130 of the holder 2120. The holder2120 and retainer ring 2122 are made of an insulating material. In someembodiments, an elastomeric material 2140, 2142 is provided in the formof an “O” ring or an annular washer, so that the fluid lens is supportedin a desired orientation, without being subjected to excessivecompressive forces or to mechanical disturbances that can beaccommodated by the elastomeric ring 2140, 2142. In some embodiments, asingle elastomeric ring 2140 or 2142 is provided on one side of thefluid lens body 2120. In some embodiments, one elastomeric ring 2140 isprovided on one side of the fluid lens body 2120, and a secondelastomeric ring 2142 is provided on the other side of the fluid lensbody. Electrical contact with the contacts 2114 and 2116 is provided bywires 2114′ and 2116′ that contact the respective contacts and whichexit the holder. These wires are in intimate electrical contact with theelastomeric material 2122 and 2140. As needed, wires 2114′ and 2116′ canbe insulated. FIG. 28 c shows the elastomeric washer 2140, which in someembodiments can be conductive, in contact with a fluid lens body 2112 atan electrical contact 2116 thereof, which fluid lens body 2112 issupported in a holder 2120 at a partially closed end 2132 thereof. Awire 2116′ contacts the conductive elastomeric washer or ring 2140 andexits the holder 2120 by way of an aperture 2134 defined within theholder 2120. In some embodiments, the wire 2116′ contacts the electricalcontact of the fluid lens body, and the elastomeric ring or washer ispositioned between the wire 2116′ and the partially closed end 2132 ofthe holder 2120. In other embodiments, the wire 2116′ is between theelastomer 2140 and the partially closed end 2130. The holder 2120 andthreaded ring 2122 can be constructed of any suitable material, and canbe non-conductive or conductive as appropriate.

The present invention also deals with the deleterious effects of imagesmear caused by hand jittering or hand motion in a hand held imager orreader. Image smear has been one of the major sources for image qualitydegradation. Image smear and similar degradation mechanisms cause areduced decode rate in a barcode reading application or a reducedcontrast and a blurry image in an image capturing application. In someinstances, hand jitter or hand motion can cause image degradation thatmay be severe enough to prevent the image from being processedcorrectly.

FIG. 29 is a diagram illustrating a prior art variable angle prism asdisclosed in U.S. Pat. No. 6,734,903 to Takeda, et. al. (hereinafter“the '903 patent”). The apparatus disclosed employs two angular velocitysensors, two angular sensors, two actuators and a variable angle prismwith a lens system to form an anti-shaking optical system. This type ofoptical system is widely used in hand held video camcorders to correctthe hand jittering effect. However, such systems suffer from a varietyof drawbacks, including: 1. higher cost due to many parts; 2. slowresponse time due to the use of mechanical actuators; 3. lowerreliability due to moving parts; 4. the use of a separate auto-focusingelectromechanical subsystem that further increases the cost and systemcomplexity; and 5. the use of mechanical components that increases thecomplexity and difficulty of assembly.

The '903 patent describes the operation of the variable angle prism asis expressed in the following 11 paragraphs.

A camera shake is a phenomenon in which photographed images movevertically or horizontally while a user is performing photographing byholding a video camera in his or her hands, since the hands or the bodyof the user slightly moves independently of the user's intention. Imagesthus photographed can give a viewer considerable discomfort whenreproduced on a television monitor or the like.

To avoid this camera shake phenomenon, conventional video cameras makeuse of, e.g., a variable angle prism (to be referred to as a “VAP”hereinafter).

A practical example of an arrangement of a conventional image sensingapparatus including a VAP for camera shake correction will be describedbelow with reference to FIG. 29.

In FIG. 29, a VAP 2204 is constituted by coupling two glass plates 2204a and 2204 b via a bellows-like spring member 2204 c and sealing anoptically transparent liquid 2204 d in the space surrounded by the twoglass plates 2204 a and 2204 b and the spring member 2204 c. Shafts 2204e and 2204 f provided in the glass plates 2204 a and 2204 b areconnected to an actuator 2203 for horizontal driving and an actuator2208 for vertical driving, respectively. Therefore, the glass plate 2204a is rotated horizontally, and the glass plate 2204 b is rotatedvertically.

Note that the VAP 2204 is described in Japanese Patent Laid-Open No.2-12518 and so a detailed description thereof will be omitted.

A horizontal angular velocity sensor 2201 detects an angular velocitycaused by a horizontal motion of the image sensing apparatus resultingfrom a camera shake or the like. A control unit 2202 performs anarithmetic operation for the detection signal from the angular velocitysensor 2201 such that this horizontal motion of the image sensingapparatus is corrected, and detects and supplies an accelerationcomponent to the actuator 2203. This actuator 2203 drives the glassplate 2204 a of the VAP 2204 horizontally.

The rotational angle of the glass plate 2204 a which can be horizontallyrotated by the actuator 2203 is detected by an angle sensor 2205. Thecontrol unit 2202 performs an arithmetic operation for this detectedrotational angle and supplies the result to the actuator 2203.

A vertical angular velocity sensor 2206 detects an angular velocitycaused by a vertical motion of the image sensing apparatus resultingfrom a camera shake or the like. A control unit 2207 performs anarithmetic operation for the detection signal from the angular velocitysensor 2206 such that this vertical motion of the image sensingapparatus is corrected, and detects and supplies an accelerationcomponent to the actuator 2208. This actuator 2208 drives the glassplate 2204 b of the VAP 2204 vertically.

The rotational angle of the glass plate 2204 b which can be verticallyrotated by the actuator 2208 is detected by an angle sensor 2209. Thecontrol unit 2207 performs an arithmetic operation for this detectedrotational angle and supplies the result to the actuator 2208.

An image sensing optical system 2210 forms an image of an object to bephotographed on an image sensor 2211. This image sensor 2211 isconstituted by, e.g., a CCD. A two dimensional solid state CCD is usedin conventional image sensing apparatuses such as video cameras. Anoutput from the image sensor 2211 is output to a recording apparatus ora television monitor through a signal processing circuit (not shown).

In the conventional image sensing apparatus with the above arrangement,the horizontal and vertical angular velocities caused by a camera shakeare detected. On the basis of the angular velocities detected, theactuators move the VAP horizontally and vertically to refract incidentlight, thereby performing control such that the image of an object to bephotographed does not move on the image sensing plane of the imagesensor. Consequently, the camera shake is corrected.

In the current invention, a fluid lens provided with additionalcomponents to counteract involuntary motions (“an anti-hand-jitteringfluid lens”) combines the auto-focusing and variable angle prismfunctionality into a single low cost component that has no moving parts,and that provides fast response time.

FIG. 30 is a cross-sectional diagram 2300 of a prior art fluid lens thatis described as operating using an electrowetting phenomenon. The fluidlens 2300 is a substantially circular structure. The fluid lenscomprises transparent windows 2302, 2304 on opposite sides thereof. InFIG. 30, a drop of conductive fluid 2360 (such as water), possiblyincluding dissolved electrolytes to increase conductivity, or to adjustthe density of the conductive fluid to match the density of anotherfluid 2370 that is immiscible with the conductive fluid (such as oil),is deposited on a surface, such as a window. A ring 2310 made of metal,covered by a thin insulating layer 2312 is adjacent the water drop. Avoltage difference is applied between an electrode 2320 (that can alsobe a ring) and the insulated electrode 2310, as illustrated by thebattery 2330. In some embodiments, an insulating spacer 2335 (not shown)is located between the rings 2310 and 2320. The voltage differencemodifies the contact angle of the liquid drop. The fluid lens uses twoisodensity immiscible fluids; one is an insulator (for example oil)while the other is a conductor (for example water, possibly with a saltdissolved therein), which fluids touch each other at an interface 2340.The variation of voltage leads to a change of curvature of thefluid-fluid interface 2340, which in turn leads to a change of the focallength or power of the lens as a result of the refraction of light as itpasses from one medium having a first optical index to a second mediumhaving a second, different, optical index. In the embodiment shown, anoptical axis 2350 is indicated by a dotted line lying substantiallyalong an axis of rotation of the fluid lens 2300. Although the power ofthe fluid lens, or its focal length, can change by application ofsuitable signals to the rings 2310 and 2320, which signals cause thecurvature of the interface 2340, in the embodiment shown in FIG. 30there is no convenient way to cause the optical axis to deviate awayfrom the axis of rotation of the fluid lens in a deliberate manner or bya desired angle.

The current invention uses the principle of altering the interface shapebetween two fluids and provides another voltage (or other suitable fluidlens control signal) to control an optical tilt of the fluid interfaceto adjust an exit optical axis angle or direction relative to the fluidlens. One application of such adjustment of the exit optical axis angleis to provide a mechanism and method to compensate the angular movementcaused by hand-jittering or hand motion.

FIG. 31 a is a cross sectional diagram 2400 showing an embodiment of afluid lens configured to allow adjustment of an optical axis, and FIG.31 b is a plan schematic view of the same fluid lens. FIG. 31 bindicates that the two metal ring electrodes 2310, 2320 of the prior artfluid lens shown in FIG. 30 have been divided into a plurality ofsegments, for example four arc pairs (2410 a, 2420 a), (2410 b, 2420 b),(2410 c, 2420 c) and (2410 d, 2420 d). A plurality of controllablesignal sources, such as voltage sources V1, V2, V3, and V4, areprovided, such that each controllable signal source can impress a signalon a selected pair of electrodes independent of the signal applied toany other electrode pair. In order to generate a desired curvature ofthe fluid interface 2440 in the fluid lens 2400, one can control allfour voltage controls V1, V2, V3, and V4 to apply a uniform focusingvoltage Vf. In this mode of operation, the fluid lens 2400 functions inexactly the same manner as the prior art fluid lens shown in FIG. 30.However, to generate an optical tilt (or to adjust an optical axis ofthe fluid lens 2400) using the fluid lens of the current invention, inone embodiment, a horizontal tilt voltage dh and a vertical tilt voltagedv are applied on each of the voltage controls by superimposing the tiltvoltages on top of the focusing voltage Vf according to the followingequations:V1=Vf+dvV2=Vf+dhV3=Vf−dvV4=Vf−dh

Application of these new signals V1, V2, V3 and V4 creates atwo-dimensional tilted fluid lens, in which horizontal and vertical tiltangles are determined according to the magnitudes and signs of thecontrol voltages dh and dv. One can generate such signals involvingsuperposition of a signal Vf and an adjusting signal using well knowncircuits that are referred to as “summing circuits” in analog circuitdesign, and by using a digital controller such as a microprocessor-basedcontroller and a digital-to-analog converter to generate suitable fluidlens control signals using digital design principles. In FIG. 24A, fluidlens surface 2445 is shown with a tilt in the vertical dimension causedby application of a signal dv as indicated for V1 and V3. The opticalaxis 2450 of the undeviated fluid lens is shown substantially along theaxis of rotation of the fluid lens, and the deviated or adjusted opticalaxis is shown by dotted line 2455, which is asymmetric with regard tothe axis of rotation. Notice that surface 2445 not only providesfocusing curvature to provide a desired optical power of focal length,but also pervades a mechanism to adjust the optical axis to correct forthe hand jittering or hand motion. In other embodiments, otherapplications can be contemplated. As an example, one can set the focallength of the lens to a small value (e.g., operate the lens as a“fisheye” lens that has a wide field of view and great depth of field)and use the adjustment of the optical axis to tip the field of view tobring some feature of interest within the field of view closer to thecenter of the field of view. In a fisheye lens, features in the centerof the field as observed with minimized optical distortions relative tothe edge of the field of view, so the object of interest can be observedwith reduced distortion. Additionally, a fisheye lens typically spreadsout objects at the edge of the field of view, so such operation canincrease the number of pixels that the object of interest occupies on aplanar image sensor, thereby increasing the detail that may be resolved.

FIG. 32 is a schematic diagram 2500 showing the relationships between afluid lens and various components that allow adjustment of the opticalaxis direction. The optical axis control system comprises a horizontalangular velocity sensor 2510, a control module 2512 to generatehorizontal tilt voltage dh, a vertical angular velocity sensor 1520, acontrol module 2522 to generate vertical tilt voltage dv, anauto-focusing control module 2530 to generate a focusing voltage Vf, adistributor module 2540 to synthesize the control voltages to controlthe fluid lens module 2400 to accommodate or to correct for handjittering. Alternately when the axis of the optical system changesorientation, the image on the image sensor will move. The processor canextract the magnitude and direction of motion of the object that was notexpected to move. This can be used as input to the correction circuit.

In some embodiments, the angular velocity sensors 2510 and 2520 arecommercially available low cost solid-state gyro-on-a-chip products,such as GyroChips manufactured by BEI Technologies, Inc., One PostStreet, Suite 2500 San Francisco, Calif. 94104. The GyroChip comprises aone piece, quartz micromachined inertial sensing element to measureangular rotational velocity. U.S. Pat. No. 5,396,144 describes arotation rate sensor comprising a double ended tuning fork made from apiezoelectric material such as quartz. These sensors produce a signaloutput proportional to the rate of rotation sensed. The quartz inertialsensors are micromachined using photolithographic processes, and are atthe forefront of MEMS (Micro Electro-Mechanical Systems) technology.These processes are similar to those used to produce millions of digitalquartz wristwatches each year. The use of piezoelectric quartz materialsimplifies the sensing element, resulting in exceptional stability overtemperature and time, and increased reliability and durability.

In other embodiments, it is possible to divide the two metal rings 2410and 2420 of FIG. 31 b into more than four symmetric arc pairs to createmore smooth tilt fluid lens. For example, one of the embodiments canhave 12 symmetric arc pairs layout in a clock numeric topology. All thesystem components shown in FIG. 32 will be the same except that theoutput of distributor 2540 will have 12 voltage control outputs to drivethe 12 arc pairs of the fluid lens module. The voltage synthesisalgorithm in distributor 2540 is based on the gradient of a (dh, dv)vector. For example, viewing the fluid lens as if it were a clock, (dh,dv)=(2.5, 0) will have a highest voltage output at a pair of electrodessituated at the 3-o'clock position and the lowest voltage output at apair of electrodes situated at the 9-o'clock position, and nosuperimposed voltage would be applied to the electrode pairs nearest the12-o'clock and 6-o'clock positions. It is possible to interpolate thegradient across any intermediate pairs of electrodes around the circleso as to apply a smoothly varying fluid lens control signal. Inprinciple, one could build a fluid lens with as many electrode pairs asmay conveniently be provided. In some embodiments, one of the two ringelectrodes can be a continuous ring to provide a common referencevoltage for all of the pairs, one element of each pair being thecontinuous ring, which for example might be held at substantially groundpotential, for ease of mounting and assembly, if for no other reason.

FIG. 33 a is a schematic diagram of an alternative embodiment of a fluidlens 2600, and FIG. 33 b is a schematic diagram of an alternativeembodiment of a distributor module 2640. In FIG. 33 a, there are shown adesigned number of symmetric connect points on ring 2610, coupled with acontinuous ring 2620. In use, a distributor module 2640 will select apair of connect points, for example 2612 c and 2612 i, according to thevector (dh, dv) to apply a tilt voltage tv to the pair of connect points2612 c and 2612 i that are disposed symmetrically about a center 2630 ofthe fluid lens. The voltage signals that will be applied are (Vf+tv,Vf−tv). The tilt voltage tv is a function of (dh, dv) and can bepredetermined by a mathematical formula or a lookup table. By selectinga material having suitable conductivity (or resistivity) for the ring2610, the voltage can be made to drop uniformly from point 2612 c topoint 2612 i along the ring 2610 such that a voltage gradient is createdto control a fluid lens having a continuously tilt along the directionof (dh, dv). In principle, the resistivity of the material should behigh, so that there is not an appreciable current flowing in the ring2610, to minimize heating and to permit a low power power supply orbattery to be used. The ring could be produced by applying a thin layerof conductive material on a nonconductive substrate that is preparedwith a desired cross sectional shape. For example, one could build aplastic ring 2610 having an inner diameter, and as appropriate, a taperor other shaped surface to match a design criterion, and then coat thesurface intended to lie adjacent the fluid with a thin layer of a highlyresistive conductor, such as carbon or tantalum, which are commonly usedas thin film resistors. Since there is an insulating layer disposedbetween the conductor and the fluid in any event, the insulating layercould additionally provide mechanical protection for the thin conductivelayer.

FIG. 34 is a schematic diagram showing the relationship between a fluidlens 2700 and a pair of angular velocity sensors. In a preferredembodiment, two of the angular velocity sensors 2710, 2720 can beintegrated with the fluid lens 2700 to form an integrated module 2730.The angular velocity sensors 2710 and 2720 are arranged in an orthogonalrelationship to detect two orthogonal angular velocities. In someembodiments, the entire control circuitry as shown in FIG. 32 can alsobe integrated into the module 2730. An advantage of this embodiment isease of mouting the module 2730. No vertical or horizontal alignmentsare required. The module will automatically adjust the lens tilt angleaccording to the output voltages dh and dv provided by the angularvelocity sensors 2710 and 2720.

FIGS. 35A-35E are cross-sectional diagrams of another prior art fluidlens that can be adapted for use according to the principles of theinvention. FIG. 35A is a cross-sectional view of a prior art fluid lenshaving no control signal applied thereto and exhibiting divergence oftransmitted light. FIG. 35B is a cross-sectional view of a prior artfluid lens having a control signal applied thereto and exhibitingconvergence of transmitted light. FIGS. 35C, 35D, and 35E arecross-sectional images of fluid lenses having convex, flat and concaveinterface surfaces as viewed from a position above each lens,respectively.

In one embodiment, using a device comprising a fluid lens, an imagesensor, and a suitable memory, it is possible to record a plurality offrames that are observed using the fluid lens under one or moreoperating conditions. The device can further comprise a computationengine, such as a CPU and an associated memory adapted to recordinstructions and data, for example for processing data in one or moreframes. The device can additionally comprise one or more controlcircuits or control units, for example for controlling the operation ofthe fluid lens, for operating the image sensor, and for controllingsources of illumination. In some embodiments, there is a DMA channel forcommunicating data among the image sensor, the CPU, and one or morememories. The data to be communicated can be in raw or processed form.In some embodiments, the device further comprises one or morecommunication ports adapted to one or more of hard-wired communication,wireless communication, communication using visible or infra-redradiation, and communication employing networks, such as the commercialtelephone system, the Internet, a LAN, or a WAN.

In this embodiment, by applying suitable selection criteria, one can useor display only a good frame or alternatively a most suitable frame ofthe plurality for further data manipulation, image processing, or fordisplay. According to this aspect of the invention, the device canobtain a plurality of frames of data, a frame being an amount of datacontained within the signals that can be extracted from the imager in asingle exposure cycle. The device can assess the quality of each of theframes against a selection criterion, which can be a relative criterionor an absolute criterion. Examples of selection criteria are an averageexposure level, an extreme exposure level, a contrast level, a color orchroma level, a sharpness level, a decodability level of a symbol withina frame, and a level of compliance of an image or a portion thereof witha standard. Based on the selection criterion, the device can beprogrammed to select a best or a closest to optimal frame from theplurality of frames, and to make that frame available for display, forimage processing, and/or for data manipulation. In addition, theoperating conditions for the device can be monitored by the controlcircuit, so that the conditions under which the optimal frame wasobserved can be used again for additional frame or image acquisition.

In alternative embodiments, it is possible to use the plurality offrames as a range finding system by identifying which frame is closestto being in focus, and observing the corresponding focal length of thefluid lens. In such an embodiment, the fluid lens can be operated so asto change its focal length over a range of focal lengths, from infinityto a shortest focal length. The device can obtain one or more frames ofdata for each focal length that is selected, with the informationrelating to each focal length being recorded, or being computable from adefined algorithm or relationship, so that the focal length used foreach image can be determined. Upon a determination of an object ofinterest within a frame (or of an entire frame) that is deemed to be inbest focus from the plurality of frames, the distance from the device tothe object of interest in the frame can be determined from theinformation about the focal length setting of the fluid lenscorresponding to that frame. In some instances, if two adjacent framesare deemed to be in suitable focus, the distance may be taken as theaverage of the two focal lengths corresponding to the two frames, oralternatively, additional frames can be observed using focal lengthsselected to lie between the two adjacent frames, so as to improve theaccuracy of the measurement of distance.

In another embodiment, apparatus and methods are provided to counteractchanges in the environment that surrounds an apparatus comprising afluid lens. In one embodiment, the apparatus additionally comprises atemperature sensor with a feed back (or feed forward) control circuit,to provide correction to the fluid lens operating signal as thetemperature of the fluid lens (or of its environment) is observed tochange.

Feedback systems rely on the principle of providing a reference signal(such as a set point) or a plurality of signals (such as a minimum valueand a maximum value for a temperature range) that define a suitable or adesired operating parameter (such as a temperature or a pressure), andcomparing a measured value of the parameter to the desired value. When adeviation between the observed (or actual) parameter value and thedesired parameter value is measured, corrective action is taken to bringthe observed or actual value into agreement with the desired parametervalue. In the example of temperature, a heater (such as a resistanceheater) or a cooling device (such as a cooling coil carrying a coolantsuch as water) can be operated to adjust an actual temperature. Using afeedback loop, the apparatus is made to operate at the desired setpoint, or within the desired range. Feedback loops can be provided usingeither or both of digital and analog signal processing, and using one ormore of derivative, integral and proportional (“D-I-P”) controllers.

In some embodiments, a feed-forward system can be used, in which achange (or a rate of change) of a parameter such as actual or observedtemperature is measured. Corrective action is taken when it is perceivedthat a condition outside of acceptable operating conditions likely wouldbe attained if no corrective action were to be applied and the observedchange (or rate of change) of the parameter were allowed to continueunabated for a further amount of time. Feed-forward systems can beimplemented using either or both of digital and analog signalprocessing. In some systems, combinations of feedback and feed-forwardsystems can be applied. In some embodiments, multiple feedback andfeed-forward controls can be implemented.

In the embodiment contemplated, the operating parameter, such astemperature, of the apparatus comprising a fluid lens, or of theenvironment in which it is situated, is monitored, and the observedparameter is compared to one or more pre-defined values. The one or morepredefined values may be fixed (such as a maximum tolerable temperatureabove which a substance begins to degrade at one atmosphere of pressure)or the one or more predefined values may depend on more than oneparameter, such as the combination of pressure and temperature, forexample using relationships in a pressure-temperature-composition phasediagram (for example, that a substance or chemical composition in thefluid lens apparatus undergoes a phase change if the pressure andtemperature vary such that a phase boundary is crossed, or undergoes achange from covalent to ionic character, or the reverse).

In yet another embodiment, a system comprising a fluid lens additionallycomprises a non-adjustable lens component configured to correct one ormore specific limitations or imperfections of the fluid lens, such ascorrecting for color, spherical, coma, or other aberrations of the fluidlens itself or of the fluid lens in conjunction with one or more otheroptical components. By way of example, a fluid lens may exhibitdispersive behavior or color error. In one embodiment, a second opticalelement is added that provides dispersion of the sign opposite to thatexhibited by the fluid lens, so as to correct the dispersive errorintroduced by the fluid lens. In one embodiment, the dispersive elementis a diffraction element, such as an embossed grating or an embosseddiffractive element. As will be understood, different optical materialshave different dispersive characteristics, for example, two glasscompositions can have different dispersion, or a composition of glassand a plastic material can have different dispersion. In the presentinvention, a material having a suitable dispersive characteristic, orone made to have suitable dispersive characteristics by controlling thegeometry of the material, such as in a grating or other diffractiveelement, can be used to correct the errors attributable to the fluidlens and/or the other components in an optical train.

The aberrations that are possible in a fluid lens can in principle be ofany order, much as the aberrations that are possible in the lens or thecornea of a human eye. Both a human eye and a fluid lens operate usinginterfaces between two or more dissimilar fluids. In the human eye,there are membranes that are used to apply forces to the fluids adjacentthe membranes, by application of muscle power controlled by signalscreated by the nervous system. In a fluid lens, there are forces thatare applied, in some instances to the fluid or fluids directly byelectromagnetic signals, and in some instances by forces applied totransparent membranes that are adjacent the fluids. Both kinds ofsystems can be affected by external forces, such as the force of gravityand other accelerative forces, changes in ambient or applied pressure,and changes in ambient or applied temperature.

In still another embodiment, there is provided a calibration tool,process, or method for calibrating a fluid lens. As one example, asystem comprising a fluid lens is operated at one or more knownconditions, such as one or more magnifications or one or more focallengths. For each known operating condition, an operating parameter,such as a value of the driving voltage, is observed or measured. Theobserved or measured data is stored in a memory. The data in memory isthen used to provide calibration data for application to the operationof the fluid lens.

Even if two or more nominally identical fluid lenses are provided, therecan be differences that exist in the two fluid lenses themselves, as hasbeen explained hereinbefore. When intrinsic differences between twonominally identical fluid lenses exist, application of a substantiallyidentical fluid lens control signal to the two lenses can result indifferent operative behavior for each lens. A default calibration can beprovided, for example based on a calibration performed under controlledor defined conditions. The default calibration data can be recorded andused at a later time to operate the fluid lens for which the calibrationwas obtained. Using such calibrations is an effective and efficient wayto operate a given fluid lens over a defined operating range. For manypurposes, such information is well worth having and helps to provide afluid lens that is conveniently operated in a predictable manner.Between calibration points, interpolation can be used to achieve animproved resolution. Similarly extrapolation may be used to estimate theattributes of a feature beyond the range of measured calibration data.

In addition, as has been indicated, differences may be externallyimposed, such as applied voltage, ambient or applied pressure, ambientor applied temperature, and accelerative forces. These forces may,individually and in combination, cause one fluid lens to operatesomewhat differently than a nominally identical fluid lens. When suchdifferences in operating conditions exist, application of asubstantially identical fluid lens control signal to the two lenses canresult in different operative behavior for each lens. Accordingly, itcan be helpful to provide a simple and readily applied calibrationmethod for a fluid lens, so that each lens can be calibrated andprovided with suitable fluid lens control signals to operate in adesired fashion under the particular conditions pertaining to that fluidlens.

Yet another reason for providing calibration capabilities relates tochanges in operation of a given fluid lens over time. The operation ofan individual fluid lens relies on one or more of the chemical,mechanical, and electrical properties of the components of the fluidlens, which properties may change with time and with use. For example,as indicated hereinabove, a fluid lens operating in response toelectrical signals may undergo electrochemically driven reactions in oneor more fluids. In addition, a fluid may change properties over time asa result thermal history, such as of repeated heating and cooling cyclesor exposure to extremes of temperature. As will be understood, as aproperty of one or more components of a fluid lens changes with time, itmay be advantageous to calibrate the operating conditions of interest.

In still a further embodiment, an inertial device such as anaccelerometer is provided to determine an orientation of a fluid lens,which orientation information is used to self-calibrate the fluid lens.Gravitational and other accelerative forces can cause fluids to move andchange shape at a free boundary, or a boundary where two fluids comeinto mutual contact. By way of example, consider a fluid lens thatcomprises two fluids having slightly different densities. Differentdensity implies that equal volumes of the two fluids will haveproportionately different masses, because density =mass/volume.Therefore, since Force (F)=mass×acceleration, the equal volumes of thetwo fluids will experience slightly different forces under equalacceleration, such as the acceleration of gravity, or of an externalaccelerative force applied to a container holding the two fluids. Oneconsequence of such an applied acceleration can be a change in therelative locations of the fluids, and as a result, a change in the shapeof the interface defined by the surface of contact between the twofluids. In addition, the direction of application of the accelerationwill also have a bearing on the response of the fluids. For example, anacceleration applied normal to a flat interface between the two fluidsmay have much less of an effect than an acceleration parallel to, ortangent to, a surface component of the interface between the two fluids.Since the accelerative force in general can be applied at any angle withregard to an interface between the two fluids, there will in general bedifferences in response depending on the precise orientation of theapplied accelerative force. Inertial sensors such as accelerometers andgyroscopes can be useful in determining and in tracking the position ofan object over time. Through the use of such inertial sensors, it ispossible to discern an orientation of an object, and to measure themagnitudes and directions of applied accelerative forces. It is possibleto calculate or to model how the fluids present in the lens will respondto the forces operating on the lens with knowledge of the orientation ofa fluid lens and of the external forces, including that of gravity.While the description presented hereinabove may be understood todescribe linear accelerative forces such as gravity, it is also possibleto perform both the tracking and the calculation of the responses offluids to forces having non-linear components, forces having rotationalcomponents, or time-varying forces. In some embodiments, usingappropriate sensors for various forces, one can determine the relativeorientation of the applied force and the interface between two fluids,and compute what response would be expected. As a result of thecomputation, information is provided for the timely application ofrestorative forces. For example, by modifying the magnitude and/or thefield direction of an electrical signal, if necessary as a function oftime, the expected distortion of the fluid interface can becounteracted. In one embodiment, solid state accelerometer sensors areprovided that operate at sufficiently high rates as to determine themagnitude and orientation of an external force. Accelerometers havingresponse rates of at least 10,000 Hz are available from CrossbowTechnology, Inc. located at 4145 N. First Street, San Jose, Calif.95134.

In yet an additional embodiment, in an apparatus comprising a fluidlens, the fluid lens is operated to provide corrective properties withregard to such distortions as may be caused by vibration, location ororientation of the lens, chromatic aberration, distortions caused byhigher order optical imperfections, and aberrations induced byenvironmental factors, such as changes in pressure. As has beenexplained hereinbefore, using accelerative forces as an example, thefluid lens may in some instances be subjected to various distortingforces or to forces that cause degradation of the operation of the fluidlens from that which is desired. In other instances, the fluid lens mayhave inherent imperfections, such as chromatic aberration or higherorder optical imperfections. It is possible to analyze such opticalimperfections in various ways, such as the use of a calibrated imagingsystem comprising a source, at least one image sensor, and hardwareand/or software configured to analyze optical information to assesswhether errors or imperfections exist in an optical component undertest. The calibrated imaging system in some instances can be alaboratory setting in which highly sophisticated equipment is employedto perform tests. In other instances, the calibrated test system cancomprise a source that provides a known optical signal that is passedthrough an optical component under test, and the analysis of theresulting signal that emerges from the optical component under test. Thecalibrated test system in some embodiments is a system or devicesuitable for use in the field, so that periodic calibration can beperformed in a convenient and efficient manner, if necessary bypersonnel who are not familiar with all of the sophistications ofoptical testing in a laboratory setting.

In one embodiment, the optical component can be modeled in the frequencydomain as a transfer function, wherein a known applied input signal I(s)is provided and an observed output signal O(s) is measured. An observedtransfer function Hobs(s)=O(s)/I(s) is determined. Hobs(s) can then becompared to a desired transfer function H(s), to determine a correctivefactor or relation C(s) that should be applied to the system under testto cause it to perform as desired, where C(s)Hobs(s)=H(s), orC(s)=H(s)/Hobs(s). Once the corrective factor or relation C(s) has beendetermined, it (or its time domain equivalent) can be applied to drivethe fluid lens so as to reduce the observed imperfection orimperfections. Transfer function concepts, discrete time mathematicalprocedures, digital filters and filtering methods, and circuitry(including hardware and software) that can handle the requireddetection, analysis and computation, and can be used to apply correctiveaction are described in many texts on real time digital signalprocessing. Hardware such as digital signal processors are commerciallyavailable from multiple vendors.

Applications for fluid lenses include their use in one or more types ofcamera, such as cameras in cell phones, use in higher quality digitalcameras such as those having a high powered zoom lens, and use incameras that can provide autofocus, and pan, tilt, and zoom (“PTZ”).Panning is moving a camera in a sweeping movement, typicallyhorizontally from side to side. Tilting is a vertical camera movement,e.g. in a direction orthogonal to panning. Commercially available PTZvideo and digital cameras that use mechanical redirection of the cameraand refocusing of its lens are well known, and are often used insurveillance. In order to accomplish such features as tilt or pan, oneneeds to reorient the interface between two optically dissimilar fluidsso that the optical axis is relocated from its original directionhorizontally (pan) or is relocated from its original directionvertically (tilt). With a fluid lens, both relocations can beaccomplished in a single redirection of the optical axis at an angle toboth the horizontal and vertical directions simultaneously. Suchredirections are readily computed using spherical geometry coordinates,but can also be computed in any coordinate system, including usingprojection from three dimensions to two dimensions, for example as iscommonly done in x-ray crystallography as an example. One method toaccomplish all of autofocus, pan, tilt, and zoom is to apply severalfeatures in a single device. Autofocus and zoom have been addressedhereinbefore. Pan and tilt, or more generally, redirection of theoptical axis to a new orientation that is non-collinear with theoriginal optical axis, can be accomplished by providing an electrodepair comprising a first plurality of first electrodes and at least onesecond electrode, and applying voltages to at least one electrode of thefirst plurality and the at least one second electrode so that thesurface shape of the interface between the two fluids in the fluid lensis caused to change a measure of asymmetry as measured with respect tothe optical axis of the fluid lens prior to the application of thevoltages. In general, to accomplish the provision of an asymmetry,either the applied voltages will include an asymmetric component, or theelectrodes to which the voltages are applied will be positioned in anasymmetric geometrical relationship, or both. By applying a voltagefield having an asymmetry to the fluids in the fluid lens, the fluidswill respond in a manner to adjust the voltage gradients across theinterface to be as uniform as possible, thereby causing the fluids totake up an interface shape that comprises an asymmetric component, andthereby directing light along a new optical axis that is non-collinearwith the optical axis that existed prior to the application of thevoltage.

We will now briefly describe examples of power supplies that are usefulfor powering a fluid lens. In one embodiment, a suitable power supplyfor driving the fluid lens is a square wave power supply that is biasedto operate in the range 0 to V volts, where V is either a positive or anegative voltage, which may be thought of as a unipolar supply. Oneembodiment is to use a bipolar power supply that is capable of providingvoltages between +V½ and −V½ volts, with an added bias voltage of +V½volts (causing the range to extend from 0 volts (=+V½ volts bias +[−V½volts] supply) to +V1 volts (=+V½ volts bias +V½ volts supply), oralternatively using an added bias voltage of −V½ volts (causing therange to extend from −V1 volts (=−V½ volts bias +[−V½ volts] supply) to0 volts (=−V½ volts bias +V½ volts supply). The summation of twovoltages is easily accomplished with a summing circuit, many variationsof which are known. In one embodiment, the bias voltage supply operatesat a fixed voltage. In other embodiments, the bias voltage supply isconfigured to provide a plurality of defined voltages, based on acommand, which may be provided by setting a switch, or under the controlof a microprocessor. In some embodiments, voltage supplies are used thatcan be controlled by the provision of a digital signal, such as adigital-to-analog converter controlled by a digital code to define anoutput signal value. In another embodiment, voltage supplies that arecontrolled using a frequency-to-voltage converter, such as the NationalSemiconductor LM2907 or LM 2917 frequency-to-voltage converter, can beemployed using a pulse train having a controllable frequency as acontrol signal. It is believed that electrochemical effects within thefluid lens are operative under sufficiently high applied voltages,thereby making the use of a unipolar supply advantageous in someinstances.

In other embodiments, power supplies that provide voltage signals havingboth positive and negative peak voltages of the order of one volt tohundreds of volts are provided. In some embodiments, the output voltagesare provided as square waves that are generated by a driver integratedcircuit such as is commonly used to operate electroluminescent lamps,such as are found in cellular telephones.

FIG. 36 is a schematic block diagram showing an exemplary fluid lensdriver circuit 2900. The circuit is powered by a battery supply 2910,typically operating in the range of 3 to 4.5 volts, although circuitsoperating with batteries of other voltages and also operating from fixedwall mount power supplies can be designed. A voltage reference 2920 isprovided which may have associated with it a low drop out voltageregulator. Input signals in the form of a clock signal (a frequency or apulse train) and digital data line are provided to a I2C serialinterface 2930 for control of this driver circuit by an external device,such as the microprocessor 1040 of FIG. 10. The serial interface 2930 isin communication with a controller 2940 (such as a commerciallyavailable microcontroller) for coordinating the activities of the fluidlens driver circuit 2900, the oscillator 2960, to set the outputfrequency, and a digital-to-analog (DAC) converter 2950, to set theoutput voltage. The DAC is provided with a reference voltage by thevoltage reference 2920. In some embodiments the DAC is a 10 bit DAC.

The controller 2940 is in communication with an oscillator 2960 thatprovides a timing signal. This oscillator 2960 can be signaled to entera power down state by a suitable signal communicated from an externalsource at 2962, which in some embodiments can be a user or can beanother controller. The controllers contemplated herein are in generalany microprocessor-based controller including a microcontroller, amicroprocessor with associated memory and programmed instructions, or ageneral purpose digital computer. The controller 2940 is also incommunication with a wave form generator 2945 that creates the squarewave waveform for the bridge driver output stage 2980. The waveformgenerator 2945 also synchronizes the DAC transitions with the outputwaveform through the controller 2940.

The output of the DAC 2950 sets the output voltage level of the highvoltage generator 2970 such that the output voltage is proportional tothe output of the DAC 2920, and thereby is configured to be controlledwith high precision by a digital source such as a computer. In someembodiments, appropriate feedback circuitry is contained in this portionof the circuit to keep the output voltage constant over a range of inputvoltage, load and environmental conditions. The high voltage created bythe high voltage generator 2970 is an input to the bridge driver 2980.The high voltage generator has a stable output ranging from 0 Volts toapproximately 40 Volts for the Varioptic ASM-1000 fluid lens. Thisgenerator may utilize an inductor 2972 and or capacitors to create thehigher voltage. However other circuit configurations might also be used,for example capacitive voltage multipliers. The bridge driver 2980creates the high voltage switching signals OUTP and OUTM which drive thefluid lens 2995. In some embodiments, the output can be applied to aload such as fluid lens 2995 using the commutating circuit of FIG. 20.

The output to the fluid lens is a voltage signal that is waveshaped bythe bridge driver using a wave form signal from the wave form generator.The term “bridge driver” should be understood as follows. The load isconnected between two amplifier outputs (e.g., it “bridges” the twooutput terminals). This topology can double the voltage swing at theload, compared to a load that is connected to ground. The ground-tiedload can have a swing from zero to the amplifier's supply voltage. Abridge-driven load can see twice this swing because the amplifier candrive either the+terminal of the load or the−terminal, effectivelydoubling the voltage swing. Since twice the voltage means four times thepower, this is a significant improvement, especially in applicationswhere battery size dictates a lower supply voltage, such as inautomotive or handheld applications.

As already indicated, one can also sum the output of the circuitdescribed with a reference signal of suitable magnitude and polarity sothat the voltage swing experienced by the load is unipolar, but of twicethe magnitude of either the positive or negative voltage signal relativeto ground. The power advantage just referred to is also present in suchan instance, because power P is given by the relationship V2/R or V2/Z,where V is voltage, R is resistance, and Z is impedance. Since thevoltage swing in both embodiments is the same v volts (e.g., from −v/2to +v/2, from 0 to +v, or from −v to 0), the power available isunchanged. Stated in terms that will be familiar to those acquaintedwith the principles of electrical engineering, since the referencevoltage of an electrical system (for example ground potential) may beselected in an arbitrary manner, merely shifting the voltages applied tothe fluid lens from one reference to a different reference should notchange the net power delivered to the fluid lens. However, whenconsidered from the perspectives of electrochemical principles, it isrecognized that different electrochemical reactions can be made to occur(or can be suppressed) depending on whether an applied electrical signalis a positive-going, or a negative-going, voltage relative to thereference voltage (e.g., polarity may be an important feature in aparticular chemical system).

FIGS. 37A and 37B are diagrams that show an LED die 3010 emitting energyin a forward direction through a fluid lens 3020. The divergence of theemitted light is modified with the fluid lens. In FIG. 37A thedivergence of the emitted light is modified because of the optical powerof the fluid lens. In the example shown the light exiting the fluid lenscould be considered to approximate collimated light even though thelight exiting the LED is diverging. In a situation where the curvatureof the fluid lens is more extreme than is shown in FIG. 37 a, the lightmay be focused on a smaller region. In FIG. 37 b the power of the fluidlens has been reduced to approximately zero so that the divergence ofthe light emitted by the LED is substantially unchanged. The comparisonof the light patterns in FIGS. 37A and 37B indicates that such systemscan be used to control the coverage (in area) at a target of interest,for example a bar code that one is interested in reading with a handheld reader or imager. In some embodiments, one or more windows on areader or scanner may also be used to protect the optical systemincluding the fluid lens from adverse environmental conditions.

It should be appreciated that although the details may change, thisconcept also applies to encapsulated LEDs, as well as to fluid lensassemblies that may contain additional optical elements such asspherical, aspherical and cylindrical lens elements.

In one embodiment, such a system is expected to more efficiently utilizea higher fraction of light emitted by the LEDs. For example when viewingbar code patterns near the imager, a more diverging illumination patternis desirable in order to be assured that larger bar code patterns areilluminated over their entire extent and when viewing bar code patternsat a larger distance from the imager, a more converging illuminationpattern is desirable so that illumination is not wasted by fallingoutside the optical field of interest.

FIGS. 38A, 38B and 38C show diagrams of a laser scanner comprising alaser 3110, a collimating lens 3120, and a fluid lens 3130 in variousconfigurations. In FIG. 38A the fluid lens is configured to have a firstoptical power, a first focal length and a first principal beamdirection. The light beam emanating from the fluid lens 3130 is focusedto have a narrowest beam width at a plane 3140 situated at a firstdistance D1 from the fluid lens 3130. In FIG. 38B the fluid lens isconfigured to have a second optical power, a second focal length and afirst principal beam direction. In FIG. 38B, the light beam emanatingfrom the fluid lens 3130 is focused to have a narrowest beam width at aplane 3141 situated at a second distance D2 from the fluid lens 3130,such that D2 is greater than D1, and the first principal beam directionis not changed when the focal length of the fluid lens 3130 is changed.In FIG. 38C the fluid lens is configured to have a first optical power,a first focal length and a second principal beam direction. In FIG. 38C,the light beam emanating from the fluid lens 3130 is focused to have anarrowest beam width at a plane 3140 situated at a first distancecorresponding to a distance D1 from the fluid lens 3130 measured alongthe second principal beam direction of FIG. 38A, but because the beam inFIG. 38C is emanating at an angle (e.g., the third principal beamdirection is not the same as the first principle beam direction), thelateral distance that the beam is “off-axis” is L1. Other opticalpowers, focal lengths and principle beam directions can be achieved byproperly configuring and energizing the fluid lens 3130.

The present inventions are intended to take advantage of fluid lens zoomoptical systems. Fluid Zoom lens configurations can be used in bar codescanners to enable imaging of different bar codes at various distancesfrom the bar code scanner. In bar code scanners manufactured today,often a large working distance is achieved by stopping down the lensaperture to increase the optical depth of field. However this has twodisadvantages: First, when the lens stop is smaller, the optical systempoint spread function increases thereby making it more difficult to scanbar code patterns with narrow bar code elements. Second, when the lensstop is smaller, less light enters the lens thereby reducing thesignal-to-noise ratio of the system. The lower SNR requires the operatorto hold the reader still for longer period of time. The effect is thatthe bar code scanner has an increased sensitivity to hand motion. Inaddition, because longer periods of time are required, the user is morelikely to become fatigued.

According to one embodiment, a sketch of zoom lens configuration 3200 isshown in FIG. 32. The object 3202 is imaged with lens assembly 3204 ontothe image plane 3206. This zoom lens makes use of 3 fluid lenses 3210,3220 and 3230. The lens system 3200 images three object points 3240,3242 and 3244 onto the image plane 3206 at the respective points 3254,3252 and 3250 respectively. Observe that because the image locations arenot resolved in this figure, the individual image points cannot be seen.The details of zoom lens 3204 are shown in more detail in FIG. 33 andthis figure show each of the lens surfaces called out for all elementsexcept the fluid lens elements that are shown in the detail of FIG. 34.

Object distance measurements can be made if the range of, or thedistance to, the object is known. A fluid lens system can be used toimplement a range finding system. In one embodiment, the fluid lenswould be focused at a number of focus positions and the position withthe best focus, as determined by any of a number of metrics, would beassociated with that fluid lens position. By knowing the fluid lensdrive voltage that caused the fluid lens to have an optimally focusedimage, and using a look-up table, the associated distance from thesystem for that specific fluid lens operating voltage can be determined.By knowing the range, the magnification can be calculated and thus theobject width associated with a given number of pixels at the imager isknown or can be deduced. In this way a system such as a bar code readeror imager can calculate the width of specific object features, such asbar code element widths or the dimensions of a package.

A fluid lens variable aperture can be added to a bar code system. Insome embodiments, the aperture would be used in the portion of theoptical system that receives light and would allow the system tooptimally trade light efficiency against point spread function width anddepth of field. When a small aperture is used, the optical system willhave a larger depth of field, but adversely the optical throughput ofthe system is reduced (i.e., less light gets through the system) and thepoint spread function (proportional to the minimal element size that canbe resolved) is also reduced. In some embodiments, a bar code system isexpected to be configured to initially have the optical system set foran optimum light throughput, and if a good read is not achieved then theaperture size could be reduced in order to extend the depth of field inan effort to decode any bar code pattern that may be within the bar codescanner field of view.

In one embodiment, a fluid lens is used as a variable aperture. FIG. 43is a diagram 4300 showing an illustrative variable aperture comprising afluid lens. One implementation of this use of a fluid lens involvesadding a colorant to at least one of the fluids to make that fluidopaque in at least a region of an electromagnetic spectral range ofinterest, such as being opaque at a specified range in the visiblespectrum. Voltage is applied to the lens from a power supply 4350 suchthat the fluid lacking the colorant that absorbs in the specified region“bottoms” against the opposite window, thereby forming a clear aperturein that spectral range of interest. An example is shown in FIG. 43,where the colorant has been added to the water component 4310 of an oil4320/water 4310 fluid lens. The fluid lens 4300 comprises metalelectrodes 4302, 4304 separated by an insulator 4306, and has a window4330 opposite the window 4340 to allow light to pass through the fluidlens 4300.

In an alternate embodiment, if the left window 4340 in FIG. 43 is curvedsuch that it is effectively parallel to the curve of the water-oilinterface, the liquid lens can in some instances be configured toperform as a variable filter. In such an embodiment, the oil would notbottom against the opposite window, but would produce a thickness of thewater that is essentially constant as a function of radius across aportion of the window. This thickness would be varied by varying theapplied voltage. The voltage-controlled thickness of the light-absorbingwater would thereby determine the amount of light passing through thefluid filter. If the colorant has light absorbing characteristics inspecific wavelengths, then the amplitude of the light in thesewavelengths passing through the fluid filter would be varied by varyingthe applied voltage.

By having more than one lens element configured as a fluid lens, forexample a lens triplet, the optical aberrations present in a singleelement can be reduced for the assemblage of lenses and this wouldresult in a higher quality optical image. The techniques for optimizinga triplet are well known in the lens design art. However, it istypically the case that any given lens is optimized for a given focallength system. Typically, if a lens is optimized for one combination ofoptical elements, it is not optimally configured when one of the lenssurfaces is changed as would happen when a single fluid element isoperated to change an optical parameter, such as a focal length. Byadding a second fluid lens, the combination of the first lens and thesecond lens can be optimized to minimize total system aberrations. Fordifferent settings of the first lens, corresponding changes in thesettings of the second lens can be made to obtain an optimalcombination. These optimized relationships between the two fluid lenssurfaces curvatures, i.e. surface optical power, and thus also thecontrol voltages, can be contained for example in a table that isrecorded in a machine readable memory. Thus for any given setting ofdesired system optical power, the appropriate drive voltages for the twofluid lenses can be developed, and applied in accordance with therecorded values. Where desirable or advantageous, the fineness of thetable resolution may be increased through use of linear or higher orderinterpolation and extrapolation.

Other prior art fluid lens systems that operate using mechanical forcesto control the shape and properties of a fluid lens are described inU.S. Pat. No. 4,514,048 to Rogers, which has already been incorporatedherein by reference in its entirety. Additional disclosure relevant tovariable focus lenses is presented in the following U.S. Pat. No.2,300,251 issued Oct. 17, 1942 to Flint, No. 3,161,718 issued Dec. 15,1964 to DeLuca, No. 3,305,294 issued Feb. 21, 1967 to Alvarez, and No.3,583,790 issued Jun. 8, 1971 to Baker, all of which are herebyincorporated by reference herein in their entirety.

Machine-readable storage media that can be used in the invention includeelectronic, magnetic and/or optical storage media, such as magneticfloppy disks and hard disks; a DVD drive, a CD drive that in someembodiments can employ DVD disks, any of CD-ROM disks (i.e., read-onlyoptical storage disks), CD-R disks (i.e., write-once, read-many opticalstorage disks), and CD-RW disks (i.e., rewriteable optical storagedisks); and electronic storage media, such as RAM, ROM, EPROM, CompactFlash cards, PCMCIA cards, or alternatively SD or SDIO memory; and theelectronic components (e.g., floppy disk drive, DVD drive, CD/CD-R/CD-RWdrive, or Compact Flash/PCMCIA/SD adapter) that accommodate and readfrom and/or write to the storage media. As is known to those of skill inthe machine-readable storage media arts, new media and formats for datastorage are continually being devised, and any convenient, commerciallyavailable storage medium and corresponding read/write device that maybecome available in the future is likely to be appropriate for use,especially if it provides any of a greater storage capacity, a higheraccess speed, a smaller size, and a lower cost per bit of storedinformation. Well known older machine-readable media are also availablefor use under certain conditions, such as punched paper tape or cards,magnetic recording on tape or wire, optical or magnetic reading ofprinted characters (e.g., OCR and magnetically encoded symbols) andmachine-readable symbols such as one and two dimensional bar codes.

Many functions of electrical and electronic apparatus can be implementedin hardware (for example, hard-wired logic), in software (for example,logic encoded in a program operating on a general purpose processor),and in firmware (for example, logic encoded in a non-volatile memorythat is invoked for operation on a processor as required). The presentinvention contemplates the substitution of one implementation ofhardware, firmware and software for another implementation of theequivalent functionality using a different one of hardware, firmware andsoftware. To the extent that an implementation can be representedmathematically by a transfer function, that is, a specified response isgenerated at an output terminal for a specific excitation applied to aninput terminal of a “black box” exhibiting the transfer function, anyimplementation of the transfer function, including any combination ofhardware, firmware and software implementations of portions or segmentsof the transfer function, is contemplated herein.

While the present invention has been particularly shown and describedwith reference to the structure and methods disclosed herein and asillustrated in the drawings, it is not confined to the details set forthand this invention is intended to cover any modifications and changes asmay come within the scope and spirit thereof.

1. A portable data collection device for imaging a target at an object distance from said device, the object distance comprising a first object distance and a second object distance that is different from the first object distance, said portable data collection device comprising: a light directing assembly for directing light toward a target; a variable focus module capturing light from the light source reflecting from the target, the variable focus module comprising a boundary element and a focus membrane communicating with said boundary element in a manner forming a fluid chamber defining an optical axis, the fluid chamber having a focus fluid disposed therein; a deforming element in communication with said focus module; and a lens controller coupled to the deforming element, the lens controller providing a control signal to said deforming element in a manner varying a force applied by said deforming element on said focus membrane in a direction parallel to the optical axis, the force adapting the focus membrane for the first object distance and the second object distance, wherein said light directing assembly comprises a first source providing light at a first wavelength and a second source providing light at a second wavelength that is different from the first wavelength.
 2. A portable data collection device according to claim 1, wherein the difference between the first object distance and the second object distance is at least 20 cm.
 3. A portable data collection device according to claim 1, further comprising at least one inelastic element positioning the deforming element relative to the deformable membrane, wherein said deforming element comprises an outer portion anchored by the inelastic element, and an inner portion moveable with respect to the outer portion.
 4. A portable data collection device according to claim 3, wherein said inner portion has a first position and a second position, the deforming element configured in a manner that causes the first position to change to the second position in response to the control signal.
 5. A portable data collection device according to claim 4, wherein the inelastic element comprises at least one contact element that conveys the control signal to the deforming element.
 6. A portable data collection device according to claim 3, further comprising: a spacer positioned between the boundary element form and the focus membrane in a manner spacing the boundary element from the focus membrane; and a pressure element adjacent the focus membrane, wherein the focus element includes at least one element configured to flex in a direction towards a pressure element in response to the control signal.
 7. A portable data collection device of claim 1, wherein the first source is an illumination source.
 8. A portable data collection device of claim 1, wherein the second source is an aimer source.
 9. A portable data collection device of claim 1, wherein the first source is an illumination source and the second source is an aimer source.
 10. A hand held reader for imaging a target at an object distance, said hand held reader comprising: a light directing assembly for directing light toward a target; an imaging assembly responsive to the light reflected by the target from the light source; a variable focus module conveying the reflected light to the imaging assembly, the variable focus module comprising a focus element having an optical axis, and a deforming element communicating with the focus element, the deforming element comprising an outer periphery and a surface extending from the outer periphery towards the optical axis in planar relation to the focus element, the surface defining an annular inner opening coaxial with the optical axis; and a control element coupled to the variable focus module, the control element comprising a lens controller providing a control signal to said deforming element in a manner varying a force applied by said deforming element along the optical axis of the focus element in the direction of a boundary element, wherein the object distance comprises a first object distance and a second object distance that is at least about 20 cm from the first object distance, and the force adapts the focus module so as to accommodate the first object distance and the second object distance, wherein said light directing assembly comprises a first source providing light at a first wavelength and a second source providing light at a second wavelength that is different from the first wavelength.
 11. A hand held reader according to claim 10, further comprising optics for distributing the light from the first source and the second source, wherein the optics comprises one or more of a collimator lens and a diffractive element positioned so as to receive the light at the second wavelength.
 12. A hand held reader of claim 10, wherein the first source is an illumination source.
 13. A hand held reader of claim 10, wherein the second source is an aimer source.
 14. A hand held reader of claim 10, wherein the first source is an illumination source.
 15. An optical system for a data reader configured for decoding an encoded indicia on a target located an object distance from the data reader, the object distance comprising a first object distance and a second object distance that is different from the first object distance, said optical system comprising: a light directing assembly for directing light toward a target; an imaging assembly responsive to the light reflected by the target from the light source; a liquid lens conveying the reflected light to the imaging assembly, the liquid lens comprising a boundary element and a deformable membrane communicating with said boundary element in a manner forming a fluid chamber having an optical axis, the fluid chamber having a focus fluid disposed therein; a deforming element adjacent the fluid chamber; a control element coupled to the deforming element, the control element comprising a lens controller providing a control signal to the deforming element deforming the deforming element relative to the fluid chamber in a manner accommodating the first object distance and the second object distance, wherein the difference between the first object distance and the second object distance is at least about 20 cm, wherein said light directing assembly comprises a first source providing light at a first wavelength and a second source providing light at a second wavelength that is different from the first wavelength.
 16. An optical system according to claim 15, further comprising at least one inelastic element positioning the deforming element relative to the deformable membrane, wherein said deforming element comprises an outer portion anchored by the inelastic element, and an inner portion moveable with respect to the outer portion.
 17. An optical system according to claim 16, further comprising: a spacer positioned between the boundary element and the deformable membrane in a manner spacing the boundary element from the deformable membrane; and a pressure element adjacent the deformable membrane, wherein the deforming element includes at least one element configured to flex in a direction towards the pressure element in response to the control signal.
 18. An optical system according to claim 15, further comprising optics for distributing the light from the first source and the second source, wherein the optics comprises one or more of a collimator lens and a diffractive element positioned so as to receive the light at the second wavelength.
 19. An optical system according to claim 15, further comprising at least one inelastic element positioning the deforming element relative to the deformable membrane, wherein said deforming element comprises an outer portion anchored by the inelastic element, and an inner portion moveable with respect to the outer portion.
 20. A optical system of claim 15, wherein the first source is an illumination source.
 21. A optical system of claim 15, wherein the second source is an aimer source.
 22. A optical system of claim 15, wherein the first source is an illumination source and the second source is an aimer source. 